Tongue fur

Also tongue coating. The normally whitish substances partially covering the upper side of the tongue. Healthy people have a thin layer of fur on their tongue, which is due to upward steaming of stomach qì. Tongue furs are categorized as glossy, dry, thick, thin, clean, slimy, grimy, and peeling. The following discussion outlines the main variations in the tongue fur and their diagnostic significance. For more detail, see tongue examination.

Nature of the Tongue Fur

It is important to observe how moist and how thick the tongue fur is, whether it is clean, slimy or grimy, and whether or not there are signs of peeling.

Moistness: A healthy tongue is kept moist naturally by saliva. A tongue covered with a transparent or semitransparent film of fluid is described as having a glossy fur and indicates damp-phlegm or cold-damp. Exuberant damp due to spleen vacuity is characterized by a slimy glossy fur in association with spleen-stomach signs of oppression in the chest, nausea, and diarrhea. Yáng vacuity water flood is marked by a glossy white tongue fur, as well as signs of cold limbs and puffy swelling. A dry fur generally indicates heat. A tongue that is so dry that it looks rough, and feels dry or even prickly to the touch, is described as being rough. It is mainly seen in externally contracted febrile diseases and indicates damage to humor by exuberant heat. However, failure of fluids to reach the upper body in patients suffering from center phlegm-damp obstruction may also cause a dry fur. In such cases, the dryness is less severe; some degree of sliminess is present and the patient experiences thirst without any urge to drink. Biomedical research shows that the moistness of the tongue depends on saliva secretion, viscosity, and evaporation speed. Dryness of the surface of the tongue is the most pronounced sign of dehydration.

Thickness: The tongue fur is regarded as thin if the underlying tongue surface shows through faintly, whereas a thick fur is one that blots out the tongue surface completely. The thickness of the tongue fur is an index of evil exuberance, progression, and regression. A thick fur indicates a strong evil, whereas a thin fur indicates a weak evil. If the fur thickens the condition is advancing; if the fur thins, it is said to be transforming, and the condition is improving. Modern research shows that the thickness of the tongue fur is associated with the length of the filiform papillae. If the papillae are long, the tongue fur is thick; if short, the fur is thin.

Clean, slimy, and grimy furs: An extremely fine fur with a grainy appearance is described as clean fur and is a normal healthy fur. If the fur is thicker, appears as a layer of mucus covering the tongue, and no longer has its normal grainy appearance, it is described as slimy fur. If the mucus layer looks dirty, the terms grimy fur, slimy fur, or turbid slimy fur are used. A slimy fur indicates damp, phlegm, and food accumulations. These evils are said to be extremely strong when the slimy coating is generalized, that is, covering the entire tongue. A slimy fur that covers only the center or the root of the tongue indicates a chronic conditionand does not transform (i.e., disappear) easily. A grimy slimy fur indicates, on the one hand, the presence of turbid evils such as turbid damp and turbid phlegm, and on the other, stomach qì vacuity. In stomach qì vacuity, attention must be paid to safeguarding stomach qì when dispelling the evil. According to the findings of modern research, slimy tongue furs are attributed to an increase in the number of filiform papillae and their branches, and the collection of mucus, putrid matter, and sloughed epithelial cells between the papillae.

Peeling: A patchy fur interspersed with mirror-like, furless areas is known as peeling fur. This generally indicates insufficiency of yīn humor and vacuous stomach qì. A peeling fur that is nontransforming and slimy fur indicates nontransformed phlegm-damp and damage to yīn humor and stomach qì, and suggests that the pattern is complex. A thick slimy fur that suddenly peels away completely indicates major damage to right qì.

Color of the Tongue Fur

White: The clinical significance of a white tongue fur is fourfold. A clean moist thin white fur is normal and healthybut may also appear at the onset of sickness indicating that the evil has not yet entered the interior and right qì remains undamaged. A glossy white fur indicates cold; thin glossy white fur indicates external wind-cold or internal cold. A thick glossy white fur indicates cold-damp or cold-phlegm. A dry white fur indicates transformation of cold evil into heat. A thin, extremely dry white fur indicates insufficiency of fluids; thick dry fur indicates transformation of dampness into dryness. A white mealy fur with a red tongue body indicates impeded damp and deep-lying heat, which is treated by first transforming the dampness to allow the heat to escape rather than with the excessive use of cool medicinals. A thick slimy white fur indicates phlegm damp and is usually accompanied by a slimy sensation in the mouth, oppression in the chest, and torpid intake. Modern research suggests that a white tongue fur is essentially normal, and that a thick white fur is mainly associated with hypertrophy of the corneal layer of the filiform papillae for unknown reasons. See also oral putrefaction and bean curd tongue fur.

Yellow fur: A yellow fur usually signifies heat. Because heat patterns vary in severity and may involve different evils, different forms of yellow fur are distinguished. A thin dry yellow fur indicates damage to liquid by heat evil, posing the need to safeguard liquid. A slimy yellow fur usually indicates damp-heat. An old yellow (i.e., dark yellow) fur and a burnt yellow (i.e., blackish yellow) fur indicate binding of repletion heat. A mixed white and yellow fur indicates the initial stages of the transformation of cold into heat that is associated with evils entering the interior. Modern research suggests that yellow fur is associated with the infectious stage of inflammatory conditions and is mainly attributable to hypoplasia of the filiform papillae, coloring by bacteria, and localized manifestation of an inflammatory disease.

Black fur: A black fur may occur in cold, heat, repletion, and vacuity patterns, but most commonly indicates an exuberant evil. A rough, dry, black fur, somewhat parched in appearance, together with a red or crimson tongue body, indicates damp-heat transforming into dryness or damage to yīn by intense heat. Usually, a thick slimy black fur indicates a phlegm-damp complication. A glossy black fur signifies either gastric or kidney vacuity. A slimy yellow fur with a grayish black coating generally indicates an exuberant damp-heat evil. A mixed gray and white fur or a gray thin slimy glossy fur generally indicates cold-damp. Modern research shows that black fur is most often seen in acute pyogenic infections, such as toxemia, gangrenous appendicitis, peritonitis, and cholecystitis. However, it may also occur in diseases such as chronic bronchitis and uremia. It mostly corresponds to what Western medicine calls a black hairy fur. Opinions differ as to the exact causes of black fur. Explanations include: growth of bacteria after long administration of antibiotics, absorption by the tongue fur of iron present in blood from minor bleeding in the oral cavity, and high fever and loss of fluid.

Etymology

Chin 舌 shé, tongue; 苔 tāi, moss, lichen.