Causes of disease originating outside the body. They include:

• The six excesses
• Epidemic qì

The Six Excesses

Early Chinese healers noted the connection between the incidence of certain illnesses and environmental conditions. They observed that wind, cold, summerheat, dampness, dryness, and heat, especially when these occurred excessively or unexpectedly, could cause diseases such as those that modern medicine calls common cold or influenza.

Basic Concepts

There are six main environmental conditions, which are called the six qì (六气 liù qì): wind, cold, summerheat, dampness, dryness, and fire (which means heat). When these give rise to illness, they are called the six excesses (六淫 liù yín).

The six excesses are variously referred to by other names:

• Because they penetrate the body and disrupt functions, they are also called evils (邪 xié).
• Because they cause illness, they are also called disease evils (病邪 bìng xié).
• Because evils are active entities, they are also called evil qì (邪气 xié qì).
• Because they enter the body from outside, the six excesses are often called externally contracted evils or simply external evils (外邪 wài xié).

The word evil is the closest English equivalent to the Chinese 邪 xié.In an apparent effort to cleanse Chinese medical discourse of the cultural metaphors, many English-language writers use terms such as pathogenic factors instead.

The illnesses caused by external evils are loosely called external contractions (外感 wài gǎn). These include

• externally contracted febrile diseases and
• non-febrile diseases affecting specific body parts or the channels and network vessels.

Externally Contracted Febrile Disease

Externally contracted febrile diseases (外感热病 wài gǎn rè bìng), often just called external contractions (外感 wài gǎn) are diseases that in most cases begin swiftly when external evils invade the exterior and give rise to heat effusion (fever) together with aversion to cold. They include what we nowadays call colds and flu but also include more serious afflictions, such as encephalitis, which begin with flu-like symptoms.

Externally contracted febrile disease is a term used in modern literature to denote diseases traditionally discussed in cold damage and warm disease theories. These are large and complex bodies of knowledge that are studied in detail after the basic theory of Chinese medicine has been mastered. See externally contracted disease pattern identification. What follows here is a brief description.

When external evils invade the body’s exterior, the body reacts by fighting them with its right qì, the forces of resistance. The struggle produces heat effusion. External evils depress the warming effect of defense yáng, so they cause aversion to cold. They also disrupt defense qì’s control over the interstices so that there is sweating or absence of sweating. The simultaneous occurrence of heat effusion and aversion to cold is the main sign of initial-stage externally contracted disease manifesting in exterior patterns.

External evils in the body’s exterior causing cold and flu are often successfully resisted by right qì and resolve within a few days. When right qì fails to resist them, they can pass into the interior, causing more severe conditions. As they penetrate the body, they undergo change. For instance, when wind-cold enters the interior, it often transforms into heat, giving rise to high fever and sometimes constipation (repletion heat patterns). If this heat damages right qì and burns itself out, the repletion heat pattern can give way to a vacuity cold pattern.

Cold damage (伤寒 shāng hán), in the broad sense, is externally contracted disease scheme devised by Zhāng Jī of the Hàn Dynasty to explain and treat it. According to cold damage theory, the external evils wind and, more importantly, cold invade the body and can affect different channels.

Usually, the evils first enter the body via the exterior, affecting the greater yáng (tài yáng) channel, which governs the exterior. This manifests in aversion to cold and heat effusion. A distinction is made between wind strike (中风 zhòng fēng) and cold damage (伤寒 shāng hán, in a narrow sense of the term) depending on the presence or absence of sweating.

The external evils can also transform into heat and pass into the exterior to affect the yáng brightness (yáng míng) channel and give rise to interior heat patterns characterized by high fever and in some cases constipation.

In some instances, the evil can affect the lesser yáng (shào yáng) channel, causing alternating aversion to cold and heat effusion, dizziness, bitter taste in the mouth, and dry throat. Lesser yáng (shào yáng) patterns are understood to be half exterior half interior, that is, mid-stage between exterior and interior.

Much less commonly, the evils can also enter the yīn channels, mostly causing interior cold patterns. For example, when the evil enters the greater yīn (tài yīn), which is related to the spleen, there may be signs such as abdominal fullness, vomiting, and diarrhea.

Warm disease (温病 wēn bìng) is externally contracted disease in the system that developed in the early Qīng Dynasty, which explains such diseases as being principally caused by warm evil (heat evil), wind, and dampness and characterized by a tendency toward dryness formation and damage to yīn. Warm disease theory developed as a rival to cold damage theory, probably in response to changes in the nature of externally contracted febrile diseases brought about by changes in climate, the growth of populations in the south, and higher population concentrations in general.

Although the doctrine identifies many different diseases, the major classifications are wind warmth, damp warmth, and warm heat.

• Wind warmth (风温 fēng wēn) is characterized by heat effusion and signs of exuberant lung or stomach heat, such as cough, rapid breathing, flaring nostrils, and thirst.
• Damp warmth (湿温 shī wēn) manifests in persistent heat effusion and signs of obstruction and stagnation caused by dampness, such as oppression in the chest, nausea, reduced eating, abdominal distension, constipation or diarrhea, and slimy tongue fur.
• Warm heat (温热 wēn rè) manifests in high fever, red complexion, thirst, maculopapular eruptions, heart vexation and, in severe cases, clouded spirit.

Like cold damage theory, the warm disease doctrine posits a progression of the disease through the body but has two distinct systems to chart it. According to one, the evil progresses through four aspects of the body: defense, qì, provisioning, and blood. The severity of the disease increases with the advance of the evil. According to the other system, progression occurs through the triple burner, starting with the upper burner and advancing to the lower burner.

Learn more about externally contracted disease in externally contracted disease pattern identification.

Nonfebrile Disease Affecting Specific Body Parts

External evils can enter the skin, specific parts of the body, and the channels, causing illnesses that are not discussed in cold damage or warm disease theory. Examples:

• impediment (bì) (corresponding to arthritis, other musculoskeletal diseases, and sciatica)
• dormant papules (urticaria)
• cinnabar toxin (dān dú, erysipelas)
• wind-fire eye (acute conjunctivitis)
• deep-source nasal congestion (paranasal sinusitis, chronic rhinitis)

Seasonality

Five of the six excesses are prevalent in a specific season: wind in spring, summerheat in summer, dampness in late summer, dryness in autumn, and cold in winter. Chinese medicine speaks of the governing qì of a specific season. All except summerheat may occur out of their normal season too. Fire is a form of heat that is not bound to any specific season.

Yīn-Yáng Classification

The six excesses can each be classified as yīn or yáng by the following criteria:

• Yīn evils reduce activity and obstruct qì, blood, and fluids, foster cold, and reduce natural loss of fluids.
• Yáng evils cause increased activity, give rise to heat, and reduce fluids.

Accordingly, wind, summerheat, and dryness are yáng, while dampness and cold are yīn. Dryness is sometimes classified as yīn because through its association with autumn, which with winter is classed as yīn.

Effects on the Body

The six excesses each affect the body in one or many ways. The effects are often interrelated, many conditions being the result of more than one effect.

Varying Susceptibility of Individuals

The susceptibility and reaction to external evils vary with the strength and nature of the individual constitution.

Strength of constitution: Healthy people are resistant to external evils; weak people are more susceptible. Healthy people have strong right qì, so when they are affected by an externally contracted evil, they can shake off the condition quickly. In less healthy people, an external contraction can linger for a long time or develop into a more severe condition.

Nature of constitution: The evils to which an individual is susceptible are also determined by the specific nature of their constitution. A person with a yīn-biased constitution is susceptible to cold, while someone who has a yáng-biased constitution is prone to heat. An individual suffering from lung qì vacuity is specifically vulnerable to wind-heat and wind-cold.

Internal Evils

In the Sòng-Jīn-Yuán (960–1368) period, medical scholars began to develop the notion that the six excesses (wind, cold, summerheat, dampness, dryness, and fire) could arise not only as external climatic influences but also within the body. This notion was fostered by the concept of the unity of Heaven (i.e., nature) and humankind, meaning that processes of the natural environment could also occur inside the human body. As the ideas were formalized, all the six excesses except summerheat became correlated with internally arising counterparts. These internal evils are often referred to as the five internal evils (内生五邪 nèi shēng wǔ xié) or simply internal evils (内邪 nèi xié).

Wind has an internal form that arises when yáng qì stirs excessively and that is associated specifically with spasm and dizziness. Only summerheat has no form that arises internally.

The distinction between external evils and evils arising internally is not always clear-cut. External dampness, for example, can affect the spleen’s ability to warm and transform water-damp, thereby fostering the development of internal dampness. People suffering from dampness arising internally from impaired splenic movement and transformation are more prone to contraction of external dampness than others. Hence, it is impossible to distinguish the two entirely. The same applies to wind, cold, dryness, and fire.

Internally arising evils, which are responsible for a variety of diseases including fright wind, wind stroke, strangury, are discussed in internal evil.

Combinations of Evils

Evils regularly combine.

• Wind regularly combines with cold or heat to form wind-cold or wind-heat, which invades the exterior to give rise to exterior patterns. It can also combine with dampness.
• Cold combines with wind or dampness.
• Summerheat and fire-heat regularly combine to give rise to summerheat-damp and damp-heat.
• Dampness combines with wind, cold, fire (heat), or summerheat.
• Dryness combines with either cold or heat.

External evils can interact with internal evils and with phlegm and static blood.

The Nèi Jīng’s Nineteen Pathomechanisms

Wind and Cold

• All fulminant rigidity is ascribed to wind 诸暴强直，皆属于风 zhū bào jiàng zhí, jiē shǔ yú
• All disease with watery humors that are clear, pure, and cold is ascribed to cold 诸病水液澄澈清冷, 皆属于寒 zhū bìng shuǐ yè chéng chè qīng lěng, jiē shǔ yú hán

Fire

• All excessive agitation and mania is ascribed to fire 诸燥狂越，皆属于火 zhū zào kuáng yuè, jiē shǔ yú huǒ
• All diseases with aching pain and swelling of the instep, and fright are ascribed to fire 诸病跗肿， 疼酸惊骇，皆属于火 zhū bìng fù zhǒng, téng suān jīng hài, jiē shǔ yú huǒ
• All heat with visual distortion and tugging is ascribed to fire 诸热瞀瘛，皆属于火 zhū rè mào chì, jiē shǔ yú huǒ
• All counterflow upsurging is ascribed to fire 诸逆冲上， 皆属于火 zhū nì chōng shàng, jiē shǔ yú huǒ
• All clenching, shuddering, and chattering [of the jaws] with the seeming loss of the spirit's presence is ascribed to fire 诸禁鼓栗，如丧神守，皆属于火 zhū jìn gǔ lì, rú sāng shén shǒu, jiē shǔ yú huǒ

Heat

• All diseases with [abdominal] sounds, where tapping makes a drum-like sound, are ascribed to heat 诸病有声，鼓之如鼓，皆属于热 zhū bìng yǒu shēng, gǔ zhī rú gǔ, jiē shǔ yú rè
• All major abdominal distension is ascribed to heat 诸腹胀大，皆属于热 zhū fù zhàng dà, jiē shǔ yú rè
• All sour retching and vomiting, and fulminant downpour with lower-body distress are ascribed to heat 诸呕吐酸，暴注下迫, 皆属于热 zhū ǒu tù suān, bào zhù xià pò, jiē shǔ yú rè
• All cramp, arched-back rigidity, and turbid watery humors are ascribed to heat 诸转反戾，水液浑浊，皆属于热 zhū zhuǎn fǎn lì, shuǐ yè hún zhuó, jiē shǔ yú rè

Dampness

• All tetany and stiffness of the neck is ascribed to dampness 诸痉项强，皆属于湿 zhū jìng xiàng jiàng, jiē shǔ yú shī

Upper and Lower Body

• All wilting, panting, and retching are ascribed to the upper body 诸痿喘呕，皆属于上 zhū wěi chuǎn ǒu, jiē shǔ yú shàng
• All reversal with constipation or diarrhea is ascribed to the lower body 诸厥固泄，皆属于下 zhū jué gù xiè, jiē shǔ yú xià

The Viscera

• All painful and itching sores are ascribed to the heart 诸痛痒疮，皆属于心 zhū tòng yǎng chuāng, jiē shǔ yú xīn
• All qì huffing and depression is ascribed to the lung 诸气膹郁，皆属于肺 zhū qì fèn yù, jiē shǔ yú fèi
• All dampness with swelling and fullness is ascribed to the spleen 诸湿肿满，皆属于脾 zhū shī zhǒng mǎn, jiē shǔ yú pí
• All wind with shaking and dizzy vision is ascribed to the liver 诸风掉眩，皆属于肝 zhū fēng diào xuàn, jiē shǔ yú gān
• All cold with contraction and tension is ascribed to the kidney 诸寒收引，皆属于肾 zhū hán shōu yǐn, jiē shǔ yú shèn

Wind

Overview of Wind

Features

• Season: mainly spring.
• Yáng evil.
• Assails the yáng regions (upper and outer body); by nature, it causes opening and discharge (sweating): Wind causes externally contracted febrile disease (colds and flu) characterized by aversion to cold with heat effusion, sweating, a floating pulse, headache, and stiff nape; itchy skin conditions.
• Mobile and changeable: Wind causes diseases that arise suddenly or change abruptly, such as externally contracted disease, itching, and wandering pain.
• Wind stirs: It causes dizziness, tremor, or even violent convulsions.
• Wind is the chief of all diseases: Wind is usually the first evil to invade the body and brings cold, heat, or dampness with it.

Wind Toxin: Causes lockjaw.

Combinations: Wind-cold, wind-heat, wind-cold-damp, wind-phlegm, wind-water.

Diseases: Common cold; dormant papules; deep-source nasal congestion; wind-fire eye; impediment; tetany; lockjaw; umbilical wind; wind stroke.

Patterns: Wind-cold fettering the exterior (or lung); wind-heat invading the exterior (or lung).

External wind is a yáng evil most common in spring. It assails the upper and outer regions of the body but also notably enters the channels. Wind is mobile and changeable in nature, giving rise to disease of swift onset and rapid development (such as common cold and flu) and conditions characterized by symptoms of changing location.

There is also internal wind arising from hyperactivity of yáng qì, from extreme interior heat in externally contracted febrile disease, or from yīn-blood vacuity (vacuity wind).

Wind is associated with spring. It affects the yáng regions of the body. It is swift and mobile, giving rise to conditions of swift onset and changing location. It causes opening and discharge of sweat. It combines with other evils such as cold, fire (heat), and dampness to invade the exterior and give rise to cold and flu. It combines with cold and dampness to invade the channels to cause impediment patterns. It can also cause itching, spasm, or paralysis.

Wind is the Governing Qì of Spring (风为春季的主气 fēng wéi chūn jì de zhǔ qì)

In China, it is most prevalent in the springtime, the time of the year when yáng qì is rising. However, it is not limited to springtime; wind disease can occur at any time of the year.

Wind is a Yáng Evil (风为阳邪 fēng wéi yáng xié)

All the features of wind are yáng in nature. It affects yáng regions of the body and is associated with movement.

Wind Assails the Yáng Regions (风易袭阳位 fēng yì xí yáng wèi); Wind By Nature Causes Opening and Discharge (风性开泄 fēng xìng kāi xiè)

Just as wind in the environment affects the upper and peripheral parts of trees and exerts its influence most strongly in high places such as mountain tops, wind as a cause of disease tends to affect the upper and outer (i.e., yáng) regions of the body. Hence, it is said that wind by nature is light and buoyant (风性轻扬 fēng xìng qīng yáng). Wind in the upper and outer parts of the body is a major cause of externally contracted febrile disease (colds and flu) manifesting in exterior patterns usually marked by a floating pulse. Wind in the skin causes itching. Wind in the external pathways of the channels can cause pain and stiff nape, back, and limbs.

Outer body: Wind affects the fleshy exterior (the fleshy outer parts of the body as opposed to the internal organs), the skin, and the limbs.

Exterior: Wind affects the fleshy exterior, causing externally contracted febrile disease. Wind in the exterior obstructs defense yáng, giving rise to heat effusion and aversion to cold, signs that, appearing together, indicate an exterior pattern. Being opening and discharging in nature, it causes the interstices (sweat glands and pores) to loosen and give rise to sweating. Because it affects the exterior, wind is reflected in a floating pulse, i.e., one that is felt at the superficial level.

Skin: When wind affects the skin, it can cause itchy skin conditions, including wheals (traditionally called dormant papules).

Channels: Wind can enter the external pathways of the channels in combination with cold and dampness, causing impediment (bì), which manifests in pain in the limbs. When wind is more pronounced than the other two evils, impediment is characterized by pain that moves from place to place, called wandering pain.

In external contractions with wind-cold fettering the exterior, the external evils can obstruct the external pathways of the greater yáng (tài yáng) bladder channel, causing headache and stiff nape.

Upper body: Wind affects the channels of the upper body and the lung.

Lung: Wind can also affect the lung, which is the uppermost viscus of the body, causing nasal congestion and runny nose, hoarse voice, itchy throat, and cough. When it affects the lung’s function of ensuring regulated flow in the waterways, wind and water can contend with each other to cause puffy swelling of the face and eyes, a condition called wind water.

Eyes: Wind can cause tearing. In conjunction with fire, it can cause wind-fire eye (roughly corresponding to acute conjunctivitis).

Channels: Wind in the channels of the upper body tends to affect the head, neck, and back, causing pain, hypertonicity, and paralysis in these areas.

Wind is Mobile and Changeable (风者善行而数变 fēng zhě shàn xíng ér shuò biàn)

Wind manifests in symptoms that move from one part of the body to another swiftly, that come and go, or that are of rapid onset and change quickly.

Common cold and flu, which are diseases marked by sudden onset, are largely ascribed in Chinese medicine to contraction of external wind, usually combined with other evils, such as cold or heat. When external wind invades the exterior, it rapidly produces a condition characterized by aversion to cold and heat effusion, sometimes with sweating. Hence, colds and flu manifesting as exterior patterns evince two qualities of wind: the tendency to affect the fleshy exterior and swift onset.

Wandering pain (游走疼痛 yóu zǒu téng tòng), i.e., pain that frequently changes location, is characteristic of impediment (bì) disease marked by a prevalence of wind over cold and dampness, which is called wind impediment. It reflects the mobile nature of wind.

Wheals (风疹块 fēng zhěn kuài): Also called hives. Localized itchy papular eruptions of the skin that appears in different places at different times. As a disease, they are called dormant papules, corresponding to urticaria in biomedicineand are attributed to wind in combination with heat or cold. Their association with itching and unfixed location reflects the changeable nature of wind.

Wind by Nature Stirs (风性主动 fēng xìng zhǔ dòng)

Wind in the environment can cause things to move; it notably causes trees and plants to bend, sway, and shake and causes leaves to swirl in the air. It can also snap tree branches so that they no longer bend and sway. Wind evil in the body produces signs characterized by movement: dizziness, shaking of the head, arched-back rigidity, convulsions, jerking sinews and twitching flesh, wriggling of the extremities, and tremor. All these except dizziness are associated with the sinews, which are governed by the liver. Hence, the Sù Wèn (Chapter 74) includes in its list of Nineteen Pathomechanisms a line that reads: All wind with shaking and dizzy vision is ascribed to the liver. Just as a powerful wind can snap the limbs of trees so that they no longer move, wind evil can cause hemiplegia and deviated eyes and mouth, and upward-staring eyes. The Sù Wènsays, All fulminant rigidity is ascribed to wind. (诸暴强直，皆属于风 zhu1 baò jiang4 zhí, jie1 shǔ yu2 fēng).

Because the sinews, which are affected by the stirring action of wind, are the body constituent of the liver, which in the five phases is related to wood, it is said that the liver is the viscus of wind and wood. In the Sòng-Jīn-Yuan2 period, the stirring of wind came to be ascribed to internal liver wind, which is described in detail in internal evil.

Wind is the Chief of the Hundred Diseases (风为百病之长 fēng wéi bai3 bìng zhi1 zhang3)

Wind tends to affect the body quicker than other evils. Cold, dampness, dryness and heat often rely on wind to enter the body. See the combinations below. Wind and the liver are mutually responsive. Affecting the liver, externally contracted wind evil can cause pain in the stomach duct, abdominal distension, rumbling intestines, retching and vomiting, and diarrhea.

Combines with Cold, Fire-Heat, Dampness, Summerheat, and Dryness

Although wind is the governing qì of spring, it can occur in any season, in combination with other evils. In fact, wind most commonly invades the body in combination with other evils, such as cold, dampness, or fire. These combinations are called wind-cold, wind-damp, wind-fire (or wind-heat), wind-dryness, and summerheat-wind (this last condition also being called summerheat tetany (暑痉 shǔ fēng), that is, summer heat giving rise to spasm).

Wind-heat and wind-cold are the main causes of exterior patterns in externally contracted disease. They also give rise to numerous other conditions:

• Wind-cold can cause cough, dizziness, dormant papules, headache, panting, and toothache.
• Wind-heat can cause deafness, dizziness, dormant papules, reddening of the eyes, and sores.
• Wind-cold-damp gives rise to impediment (bì) disease.
• Wind combines with phlegm in wind stroke and epilepsy.

Wind Toxin

A virulent form of wind is called wind toxin (风毒 fēng du2), to which lockjaw (and sometimes leprosy) are attributed. In combination with fire, it is called wind-fire toxin (风火毒 fēng huo3 du2). See toxin.

Internal Wind

Internal wind arises as a result of yīn-yáng imbalances and mostly manifests in spasm or paralysis. See internal evil.

Wind-Related Diseases

Wind is a major factor in a wide range of frequently occurring diseases:

• externally contracted febrile disease (colds, flu);
• many eye, nose, and skin conditions;
• impediment (bì);
• marked by motor disturbances, such as fright wind, lockjaw, epilepsy, and wind stroke.

For these reasons, it is said that wind is the chief of the hundred diseases. Wind-related diseases include:

Common cold (感冒 gan3 maò): This is a commonly used modern term that is also used in biomedicine, denoting a disease of sudden onset characterized by lung signs such as cough, runny nose, sneezing, and by exterior signs (aversion to cold, heat effusion). Common cold is the most common type of external contraction. It commonly takes the form of wind-cold fettering the exterior (or lung) or wind-heat invading the exterior (or lung). However, cold damage and warm disease theory make finer distinctions in externally contracted disease patterns. Cold damage theory distinguishes wind strike, in which wind is the main cause, from cold damage, in which cold is the main cause. Warm disease describes common cold manifesting in more pronounced heat signs. Note that common cold is so called in English because it is attended by aversion to cold. From the Chinese medical perspective, it is not necessarily caused by cold. More under Wind Patterns below.

Dormant papules (瘾疹 yin3 zhěn): These correspond to urticaria in biomedicine and are characterized by itchy wheals on the skin that come and go, often appearing in different places at different times. They are caused either by wind-cold or wind-heat. The distinction is made according to color. White wheals are attributed to wind-cold, while red wheals are ascribed to wind-heat.

Deep-source nasal congestion (鼻渊 bí yuan1): A disease characterized by persistent nasal congestion with turbid nasal mucus. It is attributed to wind-cold, wind-heat, or gallbladder heat. It corresponds to paranasal sinusitis or chronic rhinitis in biomedicine.

Wind-fire eye (风火眼 fēng huo3 yan3): A disease characterized by sudden reddening of the eyes. It is attributed to wind and fire. It mostly corresponds to acute conjunctivitis in biomedicine.

Impediment (痹 bì): A class of diseases arising when wind, cold, and dampness combine and invade the channels causing pain in the joints and flesh, stiffness of the joints, and sometimes numbness and tingling of the flesh. Wind, cold, and dampness all impede the flow of qì and blood, causing pain. Phlegm and blood stasis may also be factors. Signs differ depending on the prevalence of the evils. Impediment corresponds in biomedicine to arthritis, sciatica, and other musculoskeletal diseases.

• Prevalence of wind causes wandering pain. This form is called wind impediment (风痹 fēng bì) or moving impediment (行痹 xíng bì).
• Prevalence of dampness causes heaviness and pain. This form is called damp impediment (湿痹 shi1 bì) or fixed impediment (着痹 zhuo2 bì).
• Prevalence of cold causes the most intense pain. This form is called cold impediment (寒痹 han2 bì) or painful impediment (痛痹 tòng bì).
• Wind-cold-damp causing any type of impediment can transform into heat, which gives rise to vexing pain and heat in the joints. This is called heat impediment (热痹 rè bì). Phlegm and blood stasis may also be complicating factors.
• Impediment affecting the whole of the body is called generalized impediment (周痹 zhou1 bì).

Impediment is associated with loss of normal mobility, a characteristic shared by wilting (痿 wei3). However, impediment is associated with pain and numbness, while wilting is marked by weakness and limpness of especially the lower limbs. In acumoxatherapy, many acupoints treat both conditions, as indicated by the compound term wilting-impediment (痿痹 wei3 bì), which refers to weakness, pain, and numbness of the lower limbs.

Crick in the neck (落枕 laò zhěn): Stiffness of the nape and neck that results from taxation fatigue, twisting, sleeping in the wrong posture, or from exposure to wind or a draft (wind-cold).

Tetany (痉 jìng): A class of diseases characterized by severe spasm, such as rigidity of the neck and nape, clenched jaw, convulsions, and arched-back rigidity (stiff back arched backward). Tetany includes lockjaw and fright wind. Lockjaw is attributable to external wind toxin contracted through wounds. Fright wind is a disease marked by spasm developing in high fever in infants and children when externally contracted wind stirs internal wind.

Lockjaw (破伤风 pò shang1 fēng): Lockjaw (tetanus) is a disease characterized by stiff nape, facial grimace, convulsions, arched-back rigidity, upward-staring eyes, and heat effusion and aversion to cold, arising when a virulent form of external wind called wind toxin invades the body through a wound in the skin. Lockjaw in neonates is called umbilical wind.

Umbilical wind (脐风 qí fēng): Lockjaw in neonates. Umbilical wind manifests in clenched jaws, arched-back rigidity, and a peculiar grimace. In severe cases, the facial complexion is green-blue, and there is hasty breathing. It is attributable to unhygienic treatment or premature shedding of the umbilical cord. This disease has been largely eliminated by modern delivery methods.

Wind stroke (中风 zhòng fēng): A disease characterized by deviated eyes and mouth and/or clouding collapse leaving the patient with hemiplegia and deviated eyes and mouth. When deviated eyes and mouth are the only disturbance of the sinews, this is facial paralysis, which is usually attributed to external wind. Clouding collapse leaving the patient with hemiplegia and deviated eyes and mouth corresponds to what we normally call stroke (apoplexy, cerebrovascular accident). This is attributed to internal wind (usually with phlegm); see internal evil. Wind stroke in modern texts usually refers to stroke rather than facial paralysis.

Note that wind stroke means stroke, while wind strike refers to wind striking the exterior in cold damage theory. Both wind stroke and wind strike are 中风 zhòng fēng in Chinese. The use of two separate terms for the single Chinese expression helps distinguish the two distinct meanings.

Wind Patterns

Externally contracted wind evil most commonly gives rise to conditions that we normally describe as colds and flu. In Chinese medicine, these conditions are often traditionally referred to as wind damage (伤风 shang1 fēng), although modern texts nowadays tend to use common cold (感冒 gan3 maò) and flu (流行性感冒 liu2 xíng xìng gan3 maò). In the Shang1 Han2 Lun4 (On Cold Damage), they fall within the scope of greater yáng (tài yáng) wind strike or greater yang (tài yáng) cold. They affect the exterior and the lung.

Exterior signs: Contraction of external wind is invariably characterized by exterior signs, such as heat effusion and aversion to wind, sweating, and headache. The tongue fur is thin and white. The pulse is usually floating and moderate. These signs arise when wind evil assails the exterior and disturbs defense qì and the opening and closing of the interstices (sweat glands and pores).

Sweating is more likely to be present in wind-heat than in wind-cold patterns, but the strength of defense qì and state of the fluids also play a role.

Disturbances of defense qì can also give rise to maculopapular eruptions and white sweat rash.

Lung signs: Cough with expectoration of phlegm; itchy throat; sore throat; nasal congestion; sneezing; and in severe cases, rapid breathing. These signs indicate a disturbance of lung qì diffusion. See wind-cold fettering the lung and wind-heat invading the lung.

Wind evil can also disrupt not only the lung’s diffusion function but also its depurative downbearing action, giving rise to water swelling. See wind and water contending with each other.

Externally contracted wind evil patterns are discussed in detail with cold damage and warm disease theory. However, conditions can be roughly divided into wind-cold and wind-heat.

Wind-cold fettering the exterior (风寒束表 fēng han2 shù biao3): This is marked by the sudden appearance of pronounced aversion to cold, headache, and generalized pain. Other signs may include cough with clear, thin phlegm; absence of thirst; a moist, white tongue fur; and a tight floating pulse. There is usually little sweating.

The sudden onset reflects the mobile and changeable nature of wind. The floating pulse reflects wind’s tendency to affect the exterior. Sweating, if present, reflects wind’s tendency to cause opening (of the interstices) and discharge (of sweat). Aversion to cold, headache, and generalized pain reflect cold’s tendency to depress defense yáng and yáng qì in general. Depression of yáng qì also gives rise to copious clear fluids (discussed under Cold below). Most wind-cold diseases present as exterior cold patterns. See eight-principle pattern identification.

Wind-heat invading the exterior (风热犯表 fēng rè fàn biao3): Also called wind-heat assailing the exterior (风热袭表 fēng rè xí biao3). The main signs are pronounced heat effusion with mild aversion to cold (aversion to wind), headache, sweating, thirst with a liking for cool drinks, red tongue with thin dry white fur, and a pulse that is floating and rapid. Other signs include cough; sticky or yellow phlegm; painful red pharynx or red swollen tonsils. Most wind-heat diseases present as exterior heat patterns. See eight-principle pattern identification.

Wind-heat invading the exterior may be marked by headache but not by the generalized pain of wind-cold patterns. Pronounced heat effusion, thirst, sticky yellow phlegm, painful red swollen throat, and rapid pulse are all heat signs.

Cold

Overview of Cold

Features

• Season: Winter.
• Yīn evil.
• Damages yáng qì: This causes fear of cold, cold limbs, and cold pain in the abdomen that is relieved by warmth.
• Congeals and stagnates: It causes pain.
• Causes contraction and tension: Absence of sweating, tight pulse, hypertonicity of the sinews.
• Combinations: Wind-cold, wind-damp, wind-cold-damp.

Diseases: Externally contracted febrile disease (cold damage); dormant papules (urticaria); cold mounting; impediment (especially cold impediment).

Patterns: Wind-cold fettering the exterior (or lung); cold phlegm obstructing the lung; cold stagnating in the stomach and intestines; cold stagnating in the liver vessel.

External cold is a yīn evil most common in winter. It congeals and stagnates. It causes contraction and tension. It damages yáng qì. It can affect the exterior, usually in combination with wind. This is meant by cold damage in cold damage theory. It can also affect the interior directly, giving rise to what are called direct strike patterns in cold damage theory. Cold can also invade the channels, giving rise to local or generalized cold pain.

There is also internal cold, which arises within the body as a result of yáng vacuity. See internal evil.

Cold is the Governing Qì of Winter (寒为冬季的主气 hán wéi dōng jì de zhǔ qì)

Cold is the governing qì of winter. However, it can occur in any season as a result of excessive consumption of cold food and drink or foodstuffs that are cold in nature, exposure to water in a cool environment, and nowadays also air-conditioned environments.

Cold is a Yīn Evil (寒为阴邪 hán wéi yīn xié)

All of its characteristics are yīn in nature. Cold occurs in the winter, the time of the year when yīn qì is strongest. It easily damages yáng qì, and it congeals and stagnates, as well as causing contraction and tension. For these reasons, it is often referred to as yīn cold.

Cold Easily Damages Yáng Qì (寒易伤阳气 hán yì shāng yáng qì)

Cold evil gives rise to cold sensations, which are exacerbated by the fact that it easily damages yáng qì, lessening its warming action. It also reduces yáng qì’s ability to warm and transform fluids.

Palpable cold: Cold evil causes cold limbs and cold pain in the abdomen that is relieved by warmth. Hence, the Sù Wèn says: When yīn prevails, there is cold (阴胜则寒 yīn shèng zé hán).

Reduces transformation of fluids: When yáng qì is damaged, it fails to warm and transform fluids. This can result in:

• runny nose with clear snivel;
• vomiting of clear fluid;
• diarrhea with watery stool or clear-grain diarrhea (diarrhea with undigested food in the stool);
• long voidings of clear urine;

Hence, the Sù Wèn (Chapter 74) includes in its list of Nineteen Pathomechanisms a line that reads: all disease with watery humors that are clear, pure, and cold is ascribed to cold (诸病水液澄澈清冷，皆属于寒 zhū bìng shuǐ yè chéng chè qīng lěng, jiē shǔ yú hán).

Furthermore, cold also obstructs the movement of yáng qì, as discussed in the following point.

Cold Congeals and Stagnates (寒性凝滞 hán xìng níng zhì)

Cold is a yīn evil; it reduces activity, causing qì and blood to stagnate. When things that should move fail to move, pain arises. This is described in the axiom when there is stoppage, there is pain. (不通则痛 bù tōng zé tòng). Because cold causes stagnation of qì and blood, it is said, when cold prevails, there is pain (寒胜则痛 hán shèng zé tòng).

Cold evil causes pain in the area it affects, especially the chest, stomach duct, or abdomen. That pain is relieved by warmth and exacerbated by exposure to cold.

Exterior: When cold evil invades the exterior, it obstructs defense qì, preventing it from effusing to warm the fleshy exterior. This results in aversion to cold, sometimes with slight heat effusion, absence of sweating, headache, and generalized pain.

Center: When cold evil strikes the center (spleen and stomach) directly, it not only damages the spleen’s yáng qì, reducing its ability to warm and transform fluids (watery stool, clear-grain diarrhea) but also obstructs the upward bearing of spleen qì and the downward bearing of stomach qì. This manifests in vomiting of clear fluid, diarrhea with watery stool, and abdominal pain relieved by warmth, accompanied by aversion to cold and cold limbs.

Channels: When cold enters the channels and network vessels in combination with wind and dampness, it causes impediment. When cold prevails over the other two evils, giving rise to cold impediment, the pain is more pronounced than when either of the other two evils prevails.

Liver channel: Cold evil invading the liver channel can cause cold mounting, a condition attributable to cold in the umbilical region giving rise to cold sweating and counterflow cold of the limbs.

Interior: When cold evil strikes the interior directly, there is cold pain or gripping pain in the stomach duct and abdomen, rumbling intestines, and sometimes vomiting. This is called cold strike (寒中 hán zhòng) in cold damage theory.

Complexion: See next point.

Cold Causes Contraction and tension (寒性收引 hán xìng shōu yǐn)

Cold causes contraction of the interstices (sweat glands and pores), the blood vessels, and sinews.

Exterior: When cold assails the fleshy exterior, the interstices close, so there is absence of sweating. This is observed in patterns of wind-cold fettering the exterior. Note that the interstices, according to traditional theory, are the spaces in the flesh through which sweat passes outward. Although they were traditionally not believed to be confined to the skin, they are now conventionally equated to sweat ducts and sweat pores in biomedical anatomy.

Sinews: Cold evil entering the sinews causes them to contract, giving rise to hypertonicity of the sinews that manifests in inhibited bending and stretching. When cold invades the channels and joints in combination with wind and dampness, it manifests in acute pain with hypertonicity.

Vessels: Cold evil entering the blood vessels causes them to contract. This causes the pulse to become tight.

Complexion: By causing the blood vessels to contract and qì and blood to stagnate, externally contracted cold evil can cause a somber-white facial complexion and a pale tongue.

Cold’s effect of causing contraction and tension reinforces its effect of damaging yáng qì by causing congealing and stagnation of qì and blood.

Combinations and Further Developments

Cold very often enters the body in combination with wind or dampness. These conditions are called wind-cold and cold-damp.

As stated above in the discussion of wind, a combination of wind, cold, and dampness invading the channels causes impediment (bì). Prevalence of cold evil gives rise to cold impediment, which manifests in intense pain.

Cold can also combine with dryness, phlegm, and rheum. It often gives rise to congealing cold and qì stagnation, congealing cold and blood stasis. Cold damaging yáng qì can develop into vacuity cold or even yáng collapse.

If cold evil remains depressed in the body for extended periods, it can transform into heat. This may be observed in two situations:

• when, in wind-cold common cold, heat effusion and aversion to cold subside, the moist white tongue fur becomes yellow and dry, and thirst develops where previously there was none; and
• when wind-cold-damp impediment (bì) transforms into heat impediment (rè bì).

Internal Cold

Internal cold is vacuity cold stemming from insufficiency of yáng qì. See internal evil.

Cold-Related Diseases

Cold-related diseases include common cold, wind-cold dormant papules, which were discussed above under Wind above. Here we provide the further examples of cold mounting and cold impediment.

Cold mounting (寒疝 hán shan4): The term cold mounting refers to specific conditions.

• A condition of cold in the umbilical region with cold sweating and counterflow cold of the limbs, attributed to accumulation of cold evil in the abdomen arising from repeated contraction of wind-cold exacerbated by spleen-stomach vacuity or from postpartum blood vacuity.
• A condition of cold pain in the scrotum attributable to cold evil invading the reverting yīn (jué yīn) channel. The scrotum becomes swollen, hard as stone, cold, and painful. Attending signs may include impotence, fear of cold, and cold limbs. The pulse is sunken, stringlike, and tight.

Cold impediment (寒痹 hán bì): Also called painful impediment (痛痹 tòng bì). A type of impediment (chronic painful musculoskeletal conditions attributed to a combination of wind, cold, and dampness) characterized by severe articular and muscular pain and by hypertonicity and stiffness inhibiting normal movement attributed to a prominence of cold evil.

Cold Patterns

Apart from wind-cold fettering the exterior, described above under wind, several bowel and visceral patterns are caused by or may involve externally contracted cold evil. These are described in detail in bowel and visceral pattern identification but can be summarized as follows:

Heart vessel obstruction (心脉痹阻 xīn maì bì zǔ): Heart palpitation; intermittent stifling oppression and pain in the chest; blood stasis signs. Causative factors: insufficiency of yáng qì; blood stasis; phlegm turbidity; externally contracted cold or exuberant cold arising from yáng vacuity; qì depression resulting from affect damage. Note that in this pattern, externally contracted cold is only a contributory factor.

Cold phlegm obstructing the lung (寒痰阻肺 hán tán zǔ feì): Cough; panting; easily expectorated copious white phlegm; cold signs, such as cold limbs. It results from phlegm combining with externally contracted cold evil or developing with vacuity cold.

Cold stagnating in the stomach and intestines (寒滞胃肠 hán zhì weì cháng): Cold pain in the stomach duct exacerbated by cold; vomiting of clear drool; undigested food in the stool; cold signs such as cold limbs. It results from excessive consumption of raw and cold foodstuffs or catching cold in the abdomen.

Cold stagnating in the liver vessel (寒滞肝脉 hán zhì gan1 maì): Cold pain on the pathway of the liver channel with repletion cold signs, such as subjective feelings of cold and cold limbs. It is attributed to contraction of cold evil. See cold mounting above.

Summerheat

Overview of Summerheat

Features

• Season: Summer
• Yáng evil manifesting in high fever, vexation and agitation, a red facial complexion, and a surging large pulse.
• Summerheat bears upward and disperses: It causes clouded head, dizziness, and clouded spirit; it damages qì and yīn.

Internal Form: None.

Combinations: Summerheat-damp.

Diseases: Externally contracted febrile disease.

Patterns: Summerheat-heat and summerheat-damp.

Summerheat is a yáng evil that only occurs in the torrid heat of summer. It bears upward and causes clouded head and dizziness. There is no corresponding internal summerheat or vacuity summerheat.

Summerheat is the Governing Qì of Summer (暑为夏季的主气 shǔ wéi xia4 jì de zhǔ qì)

Summerheat is the governing qì of summer. It is the evil that is the most markedly seasonal in nature. It is traditionally said to occur in the six weeks following the summer solstice. The Sù Wèn (Chapter 30) says, What occurs before the summer solstice is disease attributable to warmth; what occurs after the summer solstice is disease attributable to summerheat (先夏至日者为病温, 后夏至日者为病暑 xian1 xia4 zhì rì zhe3 wéi bìng wen1, hoù xia4 zhì rì zhe3 wéi bìng shǔ). The distinction between summerheat and fire is discussed in greater detail under Fire below.

Summerheat disease includes sunstroke, an acute condition resulting from prolonged exposure to the sun. It also includes milder conditions that are not necessarily caused by direct exposure to the sun but merely by continuously elevated environmental temperatures.

Summerheat is a Yáng Evil (暑为阳邪 shǔ wéi yáng xié)

Summerheat is the torrid heat of summer. It is a yáng evil and hence manifests in yáng heat signs, such as high fever, vexation and agitation, a red facial complexion, and a large surging pulse.

Summerheat Bears Upward and Disperses (暑性升散 shǔ xìng sheng1 san4)

Summerheat bears upward means that it affects the upper body, causing clouded head and dizziness. When it affects the heart spirit, it manifests in clouding collapse (sudden loss of consciousness).

Summerheat disperses means that it causes the interstices to open and discharge. This causes great sweating that damages yīn. Because qì discharges with liquid, summerheat also gives rise to qì vacuity. The resulting pattern of dual damage to qì and yīn is characterized by fatigue and lack of strength, shortness of breath, scorching hot skin, thirst with large fluid intake, and a red tongue scantly covered with liquid.

Combines with Dampness

When the torrid heat of summer is accompanied by rain and humidity as is often the case in China, summerheat can combine with dampness to form summerheat-damp. This manifests in generalized heat failing to surface (heat that can only be felt by the hand after prolonged palpation), vexing thirst, generalized heaviness, fatigue, oppression in the chest, nausea and retching, diarrhea, and a yellow slimy tongue fur. Note that summerheat without dampness is often referred to as summerheat-heat.

Summerheat Diseases

Externally contracted febrile disease. Summerheat strike (中暑 zhòng shǔ) is the disease name given to conditions caused by summerheat. In the Jīn Guì Yao4 Lue94,it is called thermoplegia (中暍 zhòng yē).

Summerheat Patterns

Summerheat may enter the body alone or in combination with dampness.

Summerheat-heat (暑热 shǔ rè): Heat effusion, sweating or absence of sweating, red tongue with white or yellow fur, and a rapid pulse. Summerheat-heat easily damages the fluids, causing thirst with desire to drink, short voidings of yellow urine, and heart vexation. It also easily damages qì, giving rise to scantness of breath or shortness of breath, lassitude of spirit, and fatigued cumbersome limbs. Summerheat can sometimes severely obstruct the qì dynamic, causing oppression in the chest, abdominal pain, nausea and vomiting, and absence of sweating. In severe cases, it can block the heart spirit, causing clouded spirit, and even stir liver wind, causing convulsions. Clouded spirit with convulsions is often referred to as tetanic reversal.

Summerheat-damp (暑热 shǔ rè): Enduring slight heat effusion, sweating or absence of sweating, fatigued cumbersome limbs, poor appetite, oppression in the chest, nausea and vomiting, ungratifying defecation, and short voidings of reddish urine. The tongue fur is thick and slimy; the pulse is soggy.

Dampness

Overview of Dampness

Features

• Season and environments: Late summer; watery areas; other damp environments.
• Yīn evil. It obstructs movement and tends to flow downward.
• Sticky and stagnant: Obstructing qì dynamic, it causes oppression in the chest, torpid intake, and fullness and distension in the stomach duct and abdomen. Damaging yáng qì, it can cause sloppy stool, vaginal discharge, short voidings of scant urine, and water swelling.
• Heavy and turbid: it manifests in physical sensations of heaviness; it tends to flow down to the lower body; it causes foul-smelling stool, murky urine, and other turbid discharges.

Damp toxin: Causes sores, bloody stool, yellow-green vaginal discharge.

Combinations: Damp-heat, cold-damp, summerheat-damp, phlegm-damp.

Diseases: Externally contracted febrile disease (warm disease); impediment (especially damp impediment); jaundice (damp-heat or cold-damp); dysentery; damp-heat strangury; lichen; pudendal itch; damp sores; umbilical damp; scrotal wind.

Patterns: Wind and dampness contending with each other; dampness lodged in the qì aspect; damp obstruction; cold-damp encumbering the spleen; damp-heat brewing in the spleen; liver-gallbladder damp-heat; large intestine damp-heat; bladder damp-heat.

Dampness is a yīn evil associated with late summer in China and with damp and wet environments. It is sticky and stagnant, obstructing the qì dynamic and giving rise to persistent conditions. It is heavy, causing sensations of heaviness and tending to flow down to the lower body. Dampness is also described as turbid, meaning murky and unclean. It gives rise to a grimy complexion and to thick sticky dirty-looking and foul-smelling discharges and excreta.

Dampness can also form internally, but only forms repletion patterns. There is no vacuity dampness. For this reason, external and internal dampness are hard to distinguish.

Dampness is the Governing Qì of Late Summer (湿为长夏的主气 shī wéi cháng xià de zhǔ qì)

Because in most parts of China, the dampest season is the latter part of the summer, dampness is designated as the governing qì of late summer. Dampness is also associated with watery places. People living in damp climates are prone to dampness. Those who work in water, such as paddy-field workers and fishermen in any climate are prone to dampness.

Dampness is sticky and stagnant, obstructing qì dynamic and causing persistent conditions that are difficult to cure. It is also heavy and turbid: it causes physical sensations of heaviness; it tends to flow down to the lower body; it gives rise to foul-smelling stool, murky urine, and other turbid discharges. Dampness appears in externally contracted febrile disease (e.g., summerheat-damp). It can enter the channels with cold and wind to cause impediment (bì). Dampness can arise internally as a result of impaired spleen-stomach movement and transformation.

Dampness is a Yīn Evil (湿为阴邪 shī wéi yīn xié)

Dampness is sticky and stagnant and is heavy and turbid. These are all yīn qualities.

Dampness is Sticky and Stagnant (湿性黏滞 shī xìng nián zhì)

This statement has two meanings:

Dampness obstructs the qì dynamic: Dampness can obstruct the qì dynamic in any part of the body, giving rise notably to sensations of oppression, distension, fullness, and heaviness. Signs associated with different areas are as follows:

• Upper burner: Oppression in the chest, cough, and panting.
• Center burner: Distension and fullness in the stomach duct and poor appetite, sliminess or sweet taste in the mouth, and a thick slimy tongue fur.
• Lower burner: Abdominal distension and sloppy stool; inhibited urination; vaginal discharge.
• Channels and network vessels: Stiff nape and neck; sensations of heaviness (see below).
• Skin and flesh: Water-damp flooding outward into the skin and flesh can cause water swelling.

Of all these possible locations for the gathering of dampness, that of the center burner is most commonly observed in clinical practice because the spleen and stomach are especially susceptible to dampness. Furthermore, impairment of the spleen’s function of warming and transforming water-damp can cause internal dampness to arise.

Dampness causes intractable conditions: Dampness gives rise to conditions that are persistent and often difficult to treat. Examples include damp impediment (shī bì) and skin diseases caused by dampness like athlete’s foot and some forms of eczema.

Dampness is Heavy and Turbid (湿性重浊 shī xìng zhòng zhuó).

Heaviness and turbidity are two interrelated qualities of dampness.

Dampness is heavy has two meanings:

Subjective sensations of heaviness: When dampness evil invades the exterior, the patient may complain of physical fatigue, heavy cumbersome limbs, stiff nape, and heavy-headedness. The heavy-headedness attributed to dampness is often described as head heavy as if swathed (头重如裹 tóu zhòng rú guǒ).

If dampness invades the channels and joints in combination with cold and dampness, it causes impediment (bì). When dampness prevails over the other two evils, the patient complains of heavy limbs, painful joints, inhibited bending and stretching, and numbness and tingling.

Tendency to affect the lower body: Dampness is like water in that it tends to flow downwards and affect the lower body (yīn regions). It tends to pour downward into the large intestine, giving rise to diarrhea or dysentery, or into the bladder, causing turbid urine or strangury. In women, it can cause copious vaginal discharge.

Dampness is turbid: Dampness is described as turbid because it is reflected in murky, unclean excreta that are often traditionally described as foul and turbid.

• Dampness invading the upper body manifests in a dull or dirty-looking complexion, which is sometimes described as a grimy face (面垢 miàn gòu), and copious eye discharge (眵多 chī duō).
• Dampness affecting the large intestine causes diarrhea with sticky stool containing pus and blood with ungratifying defecation or tenesmus.
• Dampness affecting the bladder makes urine murky in appearance and makes urination rough and inhibited.
• Dampness pouring downward in women causes turbid vaginal discharge.
• Dampness spreading through the skin causes sores that exude sticky turbid fluid or foul turbid pus.

Damp Toxin

A virulent form of dampness is called damp toxin (湿毒 shī dú). Depending on where it accumulates, damp toxin can cause sores, bloody stool, and yellow-green vaginal discharge.

Internal Dampness

Internal dampness arises when spleen qì is unable to move and transform water-damp. Since external dampness and impaired movement and transformation are mutually conducive, it is difficult to distinguish from external dampness. External or internal dampness affecting the center tends to develop with cold or heat to give rise to cold-damp or damp-heat. See internal evil.

Combines with Wind, Cold, and Heat or Summerheat

Dampness of external origin combines with wind, cold, heat, and summerheat to create numerous different disease patterns. It also combines with phlegm.

In externally contracted febrile disease, dampness usually enters the body with fire (heat/warmth) or summerheat. Patterns include damp warmth and summerheat-damp.

External dampness in combination with wind and cold enters the body and penetrates the channels to cause wind-cold-damp impediment (bì). Prevalence of damp evil causes damp impediment, also called fixed impediment, which is characterized by heaviness and pain.

Dampness-Related Diseases

Dampness-related diseases include the following: externally contracted febrile disease (warm disease); damp impediment; damp-heat strangury; and damp skin conditions.

Damp impediment (湿痹 shī bì): Previously discussed.

Damp-heat strangury (湿热淋 shī re4 lin4): Discussed under Fire-Heat Disease further ahead.

Lichen (癣 xian3): A skin disease characterized by elevation of the skin, serous discharge, scaling, and itching. Lichen is associated with wind, heat, and dampness. Lichen characterized by dryness and scaling of the skin is called dry lichen, whereas lichen that exudes a discharge is called damp lichen.

Scab (疥 jie4): A disease characterized by small papules the size of a pinhead that are associated with insufferable penetrating itching and that, when scratched, may suppurate or crust without producing any exudate. Scab commonly occurs between the fingers and may also be observed on the inside of the elbow, in the armpits, on the lower abdomen, in the groin (inguinal region), and on the buttocks and thighs, and, in severe cases, over the whole body. It is attributed to damp-heat depressed in the skin and is transmitted by contact. In Zhu1 Bìng Yuán Hòu Lun4 (诸病源候论 The Origin and Indicators of Disease) of the Sui2 Dynasty, the author, Chaó Yuán-Fang1, attributed it to worms, which he said were small and very difficult to see. It mostly corresponds to scabies in biomedicine.

Damp sores (湿疮 shī chuang1): Any of a variety of skin diseases marked by itching, ulceration, exudation, crusting, and recurrence. They specifically include scrotal wind and umbilical damp (脐湿 qi2 shī). Acute forms are mainly ascribed to damp-heat, very often with external wind. Wind is a yáng evil, light and buoyant; it easily invades the interstices of the head, face, and upper body, carrying dampness with it.

Umbilical damp (脐湿 qi2 shī): Also called umbilical damp swelling. A condition of wetness of and possible exudation from the umbilicus, sometimes with redness and swelling of the surrounding area after the umbilical cord has been shed. Umbilical damp is attributed to the invasion of water-damp caused by improper care after removal of the cord.

Scrotal wind (肾囊风 shen4 náng feng1): A condition of dryness and itching of the scrotum relieved by bathing in hot water, and, in severe cases, with red pimples the size of millet seed that exude fluid when scratched and are sometimes associated with scorching heat pain. Scrotal wind is caused by liver channel damp-heat pouring downward and invasion of external wind evil. It is usually difficult to cure.

Pudendal itch (阴痒 yīn yang3): Itching of the female external genitals or vagina; attributed either to damp-heat pouring downward or liver-kidney yīn vacuity.

Foot qì sores (脚气疮 jiaǒ qì chuang1): Referred to biomedically as tinea pedis and colloquially in English as athelete’s foot and in East Asia as Hongkong foot. A condition of the toes and feet attributed to damp-heat pouring downward and contact with damp toxin characterized in the initial stage by water vesicles and itching between the toes and soles, and in later stages by scaling, crusting, and erosion. Foot qì sores may also give off a strange smell, which accounts for the alternate name fetid river snail (臭田螺 chòu tián luó). They are common in people who live or work in damp or wet environments and are prevalent in hot humid climates.

Dampness Patterns

The first three patterns below are caused by external dampness. The rest are patterns that are usually caused by internal dampness but may also be caused or exacerbated by external dampness. See internal evil.

Wind and dampness contending with each other (风湿相搏 feng1 shī xiang1 bó): A disease pattern arising when wind and dampness invade the body. It is described in the Shang1 Hán Lun4 (Line 175) as follows: When wind and dampness contend with each other, there is vexing pain in the joints, pulling pain and an inability to bend and stretch, pain that is exacerbated when [anyone so much as] comes near, sweating, shortness of breath, inhibited urination, aversion to cold with no desire to remove the clothes, or mild generalized swelling, Licorice and Aconite Decoction (gan1 caǒ fu4 zi3 tang1) governs.

Damp-heat lodged in the qì aspect (湿热留恋气分 shī re4 liú liàn qì fen4): In externally contracted warm disease, a pattern marked by slight heat effusion or fluctuating heat effusion, cumbersome fatigued limbs, oppression in the chest, bland or bitter taste in the mouth, thirst with no great fluid intake, short voidings of reddish urine, and a yellow slimy tongue fur.

Cold-damp encumbering the spleen (寒湿困脾 hán shī kun4 pi2): Distension and pain in the stomach duct and abdomen; nausea and vomiting; sloppy stool; signs of cold-damp collecting internally. It develops from insufficiency of spleen yáng; contraction of external dampness; or consumption of raw and cold foods.

Damp-heat brewing in the spleen (湿热蕴脾 shī re4 yun4 pi2): Glomus and distension in the stomach duct and abdomen; nausea and vomiting; bitter taste in the mouth; sloppy stool with ungratifying defecation; aversion to food; signs of damp-heat brewing internally. It develops from externally contracted damp-heat or from excessive consumption of fatty or sweet food or alcohol.

Large intestine damp-heat (大肠湿热 dà cháng shī re4): Dysentery with pus and blood in the stool or fulminant diarrhea; abdominal pain; tenesmus; and signs of damp-heat. It is caused by damp-heat brewing internally but may also result from externally contracted damp-heat or from dietary irregularities.

Liver-gallbladder damp-heat (肝胆湿热 gan1 dan3 shī re4): Distending pain in the rib-side, aversion to food, abdominal distension, yellowing of body and eyes, genital itch with signs of damp-heat. It results from external or internal dampness combining with heat.

Bladder damp-heat (膀胱湿热 páng guang1 shī re4): Urinary urgency; frequent urination; inhibited urination with scorching pain in the urethra; passing of stones with the urine; and damp-heat signs. It results from externally contracted damp-heat or from dietary irregularities giving rise to internal damp-heat that pours down into the bladder.

Dryness

Overview of Dryness

Features

• Season: Autumn.
• Yáng evil. Dryness damages the fluids.
• Dry and rough: It causes dry lips, mouth, and throat; dry cracked skin.
• Damages the lung: It causes dry cough with little or no phlegm.

Combinations: Cold, heat.

Diseases: Externally contracted disease.

Patterns: Warm dryness; cool dryness.

Dryness is a yáng evil associated in China with the autumn. It causes dry nose, mouth, and throat, as well as rough dry skin. Dryness can form internally as a result of insufficiency of the fluids.

Dryness is the Governing Qì of Autumn (燥为秋季的主气 zao4 wéi qiu1 jì de zhǔ qì)

In China, dryness is most prevalent in autumn, so it is designated as the governing qì of autumn. It is also prevalent in places with low rainfall.

Dryness is a Yáng Evil (湿为阳邪 shī wéi yáng xié)

Dryness is usually understood to be a yáng evil because like fire (the most yáng of all the evils) it manifests in damage to liquid. However, it is also argued that dryness is yīn because it belongs to autumn, which is a yīn season (the season in which yáng qì is in decline).

Dryness is Dry and Rough (燥性干涩 zao4 xìng gan1 se4)

When dryness invades the body, it damages the fluids, causing dry nose, dry pharynx, parched lips, dry cracked skin, and in some cases scant urine and dry bound stool.

Dryness Easily Damages the Lung (燥易伤肺 zao4 yì shang1 feì)

Both the lung and dryness are associated with metal among the five phases. Dryness therefore most easily affects the lung, causing dry nose and mouth and a dry cough with little or no phlegm. In some cases, there may be panting and chest pain. Note that the lung is classically said to be averse to cold.

Combinations

Heat or cold; phlegm. See Dryness Patterns below.

Internal Dryness

Internal dryness results from fluid depletion. See internal evil.

Dryness Patterns

Only one pattern results from contraction of external dryness, although it can take different forms.

Dryness evil invading the lung (燥邪犯肺 zao4 xié fàn feì): Dry throat, nose, mouth, and lips with mild heat effusion, cough with scant sticky phlegm that is difficult to expectorate, and in some cases headache. It occurs in dry weather (of autumn in China). Distinction is made between warm dryness, which in China occurs in early autumn, and cool dryness, which occurs in late autumn. The two are distinguished by heat and cold signs, respectively.

Fire

Overview of Fire

Season: Any.

Features

• Yáng evil.
• Burns and scorches: Fire manifests in high fever and damage to fluids.
• Flames upward: It gives rise to upper body signs such as clouded head and headache, dry mouth and throat, red face and eyes, erosion of mouth and tongue, painful swollen gums, and bleeding in the upper body.
• Rapidity: Fire evil invading the body causes illness that develops quickly. It causes the blood to move rapidly, giving rise to a rapid pulse and in some cases bleeding.
• Harasses the heart spirit: Fire can cause heart vexation, insomnia, manic agitation, and delirious speech.
• Stirs the blood: Fire can stir the blood, causing frenetic movement of hot blood, which manifests in various forms of bleeding (nosebleed, coughing of blood, vomiting of blood).
• Engenders wind: Extreme heat can engender wind manifesting in convulsions.
• Causes sores: Fire putrefies the flesh, giving rise to welling-abscesses and other sores.

Fire toxin: Any virulent form of fire.

Combinations: Wind, dampness. Also combines with phlegm.

Diseases: Externally contracted febrile disease (warm disease; cold damage evils transforming into heat); sores.

Patterns: Hyperactive heart fire; wind-heat invading the lung, intense lung heat, liver fire flaming upward, damp-heat brewing in the spleen, liver-gallbladder damp-heat, and intense stomach fire.

Fire is a yáng evil unassociated with any particular season. It burns and scorches, manifesting in heat signs. It flames upward, causing upper-body heat signs. It increases activity and movement, giving rise to a rapid pulse, manic agitation, bleeding, and internal wind. It damages the fluids of the body and also consumes (i.e., damages) qì. It can also damage the blood, causing putrefaction of the flesh.

Season

Fire refers to environmental heat that occurs at any time of the year. The Sù Wèn (Chapter 30, Treatise on Heat) asserts: What occurs before the summer solstices is disease attributable to warmth; what occurs after the summer solstice is disease attributable to summerheat. In this context, warmth is synonymous with fire or heat, which has characteristics that partly differ from summerheat. Although the Sù Wèn states that fire occurs at times of the year other than in the summer, it can in fact occur in any season.

Fire Burns and Scorches (火性燔灼 huǒ xìng fán zhuó)

Fire burns and scorches. Fire manifests in high fever.

Fire By Nature Flames Upward (火性上炎 huǒ xìng shàng yán)

Fire mostly affects the upper part of the body, giving rise to clouded head and headache, dry mouth and throat, red face and eyes, and bleeding in the upper body (see Fire Stirs the Blood below).

Fire By Nature is Urgent and Rapid (火性急速 huǒ xìng jí sù)

One meaning of this phrase is that fire disease develops rapidly. This characteristic is especially noticeable in warm disease. When warm evil invades the body, the patient briefly experiences slight aversion to wind or cold, which is a defense-aspect pattern. Often, the evil swiftly moves into the qì aspect, causing vigorous heat effusion, vexation and thirst, sweating, short voidings of reddish urine, red tongue with yellow fur, and a pulse that is rapid and surging. Other implications of fire’s urgency and rapidity are reflected in its propensity to stir the blood, harass the heart spirit, and engender wind, as explained below.

Fire Easily Stirs the Blood (火易动血 huǒ yì dòng xuè)

As stated, fire naturally gives rise to a rapid pulse. When it enters the blood aspect, it stirs the blood, causing it to extravasate. This is called frenetic movement of hot blood. It manifests in nosebleed, vomiting of blood, coughing of blood, bloody stool, bloody urine, and maculopapular eruptions.

Fire Harasses the Heart Spirit (火扰心神 huǒ rǎo xīn shén)

Fire often enters the provisioning aspect and harasses the spirit, causing vigorous heat effusion, manic agitation, clouded spirit, and delirious speech. As the Sù Wèn (Chapter 74) states, All excessive agitation and mania is ascribed to fire (诸燥狂越，皆属于火 zhū zào kuáng yuè, jiē shǔ yú huǒ).

Fire Easily Engenders Wind (火易生风 huǒ yì shēng fēng)

Fire can engender wind. When heat evil scorches the liver channel and damages yīn humor, it deprives the sinews of moisture and nourishment and causes wind to stir. This is called extreme heat engendering wind, described internal evil. It is characterized by vigorous heat effusion, convulsion of the limbs, rigidity of the neck, and in severe cases arched-back rigidity, upward-staring eyes, and clenched jaws.

Fire Easily Damages Liquid and Consumes Qì (火易伤津耗气 huǒ yì shāng hào qì)

When yáng prevails, yīn ails. Fire directly scorches the fluids. It steams the fluids and forces them to discharge outward in the form of sweat. This action damages the fluids of the body, causing thirst with desire for fluids, dry throat and mouth, short voidings of reddish urine, and dry bound stool.

Because heat is yáng and merges with the yáng qì of the body, it causes yáng qì to be consumed in wasteful overactivity. Thus, the Sù Wèn (Chapter 5) states, Vigorous fire consumes qì (壮火食气 zhuàng huǒ shí qì). This manifests in scantness of breath, laziness to speak, fatigue and lack of strength.

Note that summerheat also causes damage to qì and liquid.

Fire Easily Causes Sores (火易致疮痈 huǒ yì zhì chuāng yōng)

Fire can cause sores (welling-abscesses, boils, clove sores, etc.). When fire is especially intense, it is called fire toxin (火毒 huǒ dú). Fire toxin enters the blood aspect and gathers locally to cause putrefaction of the flesh and the development of pus. Such conditions manifest outwardly in redness, swelling, heat, and pain. The Sù Wèn (Plain Questions, Chapter 5) states, When heat prevails, there is swelling (热胜则肿 rè shèng zé zhǒng).

Fire Toxin

Fire toxin, also called heat toxin (火毒 huǒ dú), is a virulent form of fire that causes severe swelling and even suppuration. It is the cause of welling-abscesses and sores. Occurring in warm disease, it is called warm toxin (温毒 wēn dú) and gives rise notably to the swelling of cheeks in mumps. It is also closely associated with epidemic qì, which is discussed below.

Internal Fire

Internal fire is fire arising internally as a result of either yīn vacuity (vacuity fire) or the transformation of evils or stagnant qì (repletion fire). See internal evil.

Combines With Wind and Dampness

Among the other external evils, fire is most likely to combine with wind, the combination usually being called wind-heat. Hot humid environments can give rise to damp-heat conditions. In addition, it also combines with phlegm to produce phlegm-heat (or phlegm-fire).

Externally Contracted Fire-Heat Terms

Heat, fire, and warmth as disease evils are close synonyms. In some contexts, they each have nuanced meanings, but when emphasis is on common characteristics, the compound term fire-heat (火热 huǒ rè) is often used as an umbrella term. Because they are evils, they are often referred to as such: heat evil (热邪 rè xié), evil heat (邪热 xié rè), fire evil (火邪 huǒ xié). Summerheat, too, may be regarded as an external heat evil manifesting in heat signs. Both heat and fire can denote things other than evils. The specific connotations of fire-heat terms are as follows:

• Among the six excesses, fire is the term used, although when it occurs in combinations, it is often replaced by heat. Hence, we speak of wind-heat as a cause of exterior patterns, rather than wind-fire. However, wind-fire appears in many disease names, such as wind-fire eye (roughly corresponding to acute conjunctivitis) and wind-fire toothache. Fire and heat may also denote evils arising internally.
• Warmth (温 wēn) originally denoted a mild form of heat. The term was adopted in warm disease theory with barely any connotation of mildness. In warm disease theory, the compound term warm-heat (温热 wēn rè) emphasizes the qualitative unity of warmth and heat. Warm-heat refers exclusively to evils of external origin. There is no such thing as internal warmth or vacuity warmth.
• Summerheat is strictly associated with the torrid heat of summer. Like warm-heat, summerheat refers exclusively to an evil of external origin. There is no internal summerheat or vacuity summerheat.

Fire-Heat Diseases

Below are a few examples of the many diseases associated with fire-heat.

Externally contracted disease: Fire-heat is the main evil to which warm disease is attributed. (In cold damage, heat patterns, such as yáng ming2 (yáng ming2) disease patterns, are mostly attributed to internal fire arising through the transformation of external wind and cold into heat as they pass into the interior.)

Heat cholera (热霍乱 rè huo4 luan4): Cholera (simultaneous vomiting and diarrhea, in severe cases with cramps in the lower legs) with hot malodorous stool, heat effusion, thirst, heart vexation, reddish urine, a yellow slimy tongue fur, and a rapid surging or rapid sunken pulse.

Dysentery (痢疾 lì jí): A disease characterized by tenesmus (urgency to defecate and straining) with blood and pus in the stool (pus referring to pus-like mucus, not actual pus). Dysentery usually occurs in hot weather and arises when spleen vacuity and eating raw, cold, or unclean food allow damp-heat to arise and pour down to the intestines. When blood and pus (actually mucus) are equally prominent, it is called red and white dysentery. When either is prominent, it is called red dysentery or white dysentery. In the advanced stages, it may turn into a vacuity pattern characterized by fatigue and milder abdominal pain. This is called vacuity dysentery.

Damp-heat strangury (湿热淋 shi1 rè lin4): Often referred to simply as heat strangury (热淋 rè lin4). Dribbling urination (frequent, short, rough voidings) with scorching pain in the urethra and tension in the smaller abdomen (lower abdomen). In some cases, there is pain stretching into the lumbus or abdomen. Damp-heat strangury may be caused by dampness and heat either of external or internal origin. Distinction is made between heat strangury, stone strangury, blood strangury, and unctuous strangury. Pathomechanisms and signs differ according to the type of strangury.

Cinnabar toxin (丹毒 dan1 dú): A disease characterized by sudden localized reddening of the skin, giving it the appearance of having been smeared with cinnabar; hence the name. It corresponds to erysipelas and some forms of cellulitis in biomedicine. Cinnabar toxin usually affects the face or lower legs. It is most common among children and the elderly and most prevalent in spring and summer. Cinnabar toxin arises when damaged skin and insecurity of defense qì allow evil toxin to enter the body and give rise to heat in the blood aspect, which becomes trapped in the skin. If the toxin is accompanied by wind, the face is affected (wind-heat); if accompanied by dampness, the legs are affected (damp-heat). Note that the Chinese term丹毒 dan1 dú has been adopted as the biomedical equivalent of erysipelas, but the original Chinese concept is wider in meaning and includes cellulitis.

Lower-limb fire flow (下肢流火 xia4 zhi1 liú huǒ) is the type of cinnabar toxin that affects the lower legs and feet. It is marked by localized painful redness and diffuse swelling. It is attributed to damp-heat. See previous item.

Welling-abscess (痈 yōng): A large suppuration in the flesh characterized by painful swelling and redness that are clearly circumscribed. Before rupturing, it becomes soft and characterized by a thin shiny skin. Welling-abscesses arise when damp-heat and fire toxin cause congealing and stagnation of qì and blood that fosters putrefaction.

Abscesses within the body are called internal welling-abscesses. These include intestinal welling-abscess (肠痈 cháng yōng), which corresponds to appendicitis in biomedicine.

Boil (疖 jié): A small, round, superficial swelling that is hot and painful, suppurates within a few days, and easily bursts. It is attributable to heat toxin or to summerheat-heat and usually occurs in the summer or autumn.

Clove sore (疔疮 ding1 chuāng): A clove sore is a sore that is the size of a millet or rice grain at onset. It has a hard root that penetrates deep into the skin, and it is associated with numbness and tingling or itching. The tip is white and very painful. It is the result of the congestion of qì and blood that mostly occurs when heat brewing in the bowels and viscera combines with powerful toxins contracted through the skin.

Purulent ear (聤耳 ting2 er3): A disease characterized by the discharge of pus or pus-like yellow fluid from the ear. It is caused by fire or damp-heat.

Fire-Heat Patterns

Repletion patterns arising from externally contracted fire-heat include wind-heat invading the exterior (described under Wind above), wind-heat invading the lung, intense lung heat, as described below. For the numerous fire-heat patterns occurring in warm disease, see warm disease pattern identification.

Wind-heat invading the lung (风热犯肺 fēng rè fan4 feì): Cough with expectoration of yellow phlegm; and wind-heat exterior signs. It results from external contraction of wind-heat.

Intense lung heat (肺热炽盛 feì rè chì shèng): Cough; panting; painful swollen throat; signs of interior repletion heat. It results from: warm-heat evil invading the lung; wind-cold transforming into heat, entering the interior, and settling in the lung; or internal heat affecting the lung.

Hyperactive heart fire (心火亢盛 xīn huǒ kàng shèng): Vexation and agitation or even manic agitation and delirious speech; mouth and tongue sores; and repletion heat signs (e.g., heat effusion). Develops from: excesses among the seven affects, causing qì to become depressed and transform into fire; excessive consumption of rich, fatty, and hot spicy foods; external fire invading the interior.

Epidemic Qì 疫气 yì qì

What is Epidemic Qì?

Epidemic qì (疫气 yì qì) is the name given to evils that cause epidemic diseases, that is, highly contagious diseases. Both epidemic qì and epidemic disease are referred to by numerous names.

Epidemic Diseases

Epidemic diseases have five defining characteristics:

• Contagiousness: Epidemic diseases are communicable by close contact.
• Epidemicity: They affect a large proportion of persons in a community or area at one time.
• Severity: They are severe, and sometimes fatal.
• Rapid development: They develop rapidly after contraction.
• Similar manifestations and course in all individuals.Each epidemic disease is characterized by similar manifestations and similar courses in all affected individuals. Different epidemic diseases are attributed to different types of epidemic qì.

Epidemic qì differs from the six excesses. The latter constantly cause disease among limited numbers of any population. Epidemic qì only occurs from time to time in specific areas.

Below are some examples of epidemic diseases traditionally recognized.

Measles (麻疹 ma2 zhen3): An epidemic disease affecting mostly children below the age of puberty, characterized by eruption of papules the shape of sesame seeds. It is caused by contraction of seasonal pestilential heat toxin and mostly occurs at the end of winter or beginning of spring. The disease is located in the spleen and lung channels and can affect the other bowels and viscera.

Measles starts like a common cold, with cough, sneezing, runny nose with clear snivel, tearing, and heat effusion. After 2–3 days, a rash appears on the buccal mucosa (inside the mouth, on the cheek). After 3–4 days, the rash spreads. It is peach-pink in color, in the form of papules shaped like sesame seeds. On the outside of the body, it starts on the hairline behind the ears, gradually spreading to the forehead, trunk, and limbs.

Mumps (痄腮 zha4 sai1): Also called massive head scourge (大头瘟 da4 toú wēn) or toad head scourge (虾蟆瘟 ha2 ma2 wēn) because the neck and head resemble those of a toad. An epidemic disease most prevalent in children in winter and spring, attributed to warm toxin, and marked by diffuse painful swelling in front of the ears (now known to be swelling of the parotid glands). The wind warmth toxin evil causes accumulation of heat in the stomach and intestines and depressed liver-gallbladder fire that obstructs the lesser yáng (shào yáng).

Heaven-current red eye (天行目赤 tian1 xing2 mù chì): A contagious disease characterized by red eyes (reddening of the white of the eyes), thick sticky eye discharge, dryness that makes opening the eyes difficult, and fear of light. It can affect one eye or both. Often transmitted from one family member to another. It is similar to wind-fire eye but is more severe and contagious.

Putrefying throat sand (烂喉痧 lán hoú sha1): Corresponds to scarlatina in biomedicine. An epidemic disease attributed to pestilential toxin in the lung and stomach, prevalent in winter and spring, and characterized by painful swelling and putrefaction of the throat, sometimes with ulceration and an easily removable pseudomembrane. There is pronounced heat effusion and aversion to cold, with generalized pain. Tiny red papules called sand speckles (沙点 sha1 dian3) or cinnabar sand (丹痧 dan1 sha1) appear all over the body.

Diphtheria (白喉 baí hoú): An epidemic pestilence characterized by whitening of the throat together with headache, generalized pain, heat effusion, vexation and agitation, fetid mouth odor, and nasal congestion. It is attributed to seasonal epidemic scourge toxin exploiting vacuity of the lung and stomach.

Epidemic dysentery (疫痢 yì lì): Severe contagious dysentery characterized by abdominal pain, tenesmus, and blood and pus in the stool, together with high fever, headache, vexation and agitation, and thirst.

Smallpox (天花 tian1 hua1): An epidemic disease characterized by heat effusion, cough, sneezing, yawning, red face, fright palpitation, cold extremities and ears, and eruption of pox (a pustular eruption). Interestingly, historical records suggest that inoculation against smallpox was practiced as early as the Northern Sòng and that nasal inoculation was discovered in the Ming2 Dynasty between 1567 and 1572.

How the Concept of Epidemic Qì Developed

In ancient times, epidemics were understood to be contagious diseases caused by climatic evils, such as cold, heat, or dampness, which also caused minor ailments like colds. The greater severity and contagiousness of epidemic pestilences were explained by the greater severity of the climatic conditions and their untimeliness in the yearly cycle. In other words, outbreaks of highly contagious and often fatal diseases were attributed to spells of specifically severe cold or heat, especially when these came at unexpected times of the year.

In the 17th century (Ming2), Wú Yoù-Ke3 introduced the idea that epidemics were caused by perverse qì (戾气 lì qì, 乖戾之气 guai1 lì zhi1 qì), which were distinct from weather factors. He said that while cold damage and summerheat strike were common diseases that were directly caused by weather conditions, epidemics were caused by perverse qì that entered the body through the mouth and nose and that could infect anyone who came into contact with them, especially those in a weak state of health. He posited that numerous kinds of perverse qì existed, each causing distinct diseases characterized by different symptoms. For example, one perverse qì could give rise to disease characterized by swollen cheeks (腮肿 sai1 zhǒng) another could cause swelling of the whole head and face, another could lead to painful swollen sore throat, while others could result in disease characterized by pustules (traditionally referred to generically as pox, 痘 doù) or maculopapular eruptions. Specific kinds of epidemic qì could affect humans, plants, or animals. Wú believed that specific medicinals could effectively treat specific kinds of epidemic qì. Despite Wú’s contributions, epidemic pestilences did not entirely cease to be treated as heat, summerheat, and wind.

How Epidemic Qì Arises and Spreads

The rise and spread of epidemic qì is associated with the following climatic, hygiene, and social factors:

Climatic factors: Abnormal temperatures or drought or flooding due to abnormal rainfall levels can contribute to the development and spread of epidemic qì.

Hygiene: Unclean water and food are major conditions for the rise of epidemics. Epidemic dysentery and epidemic jaundice, for example, are both associated with unclean food.

Other factors: War and natural disasters often disrupt the provision of clean water and foodstuffs, while poverty can make them unaffordable. For these reasons, these factors often contribute to epidemics.