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Normal tongue fur is generated by stomach qi and food qi flowing up to the mouth. Morbid tongue fur is caused by stomach qi and pathogenic qi flowing to the mouth. Therefore, pathologically, tongue fur reflects the location and nature of diseases as well as the condition of healthy qi. Normal tongue fur is moist, white and thin and distributed evenly (a bit thick in the middle and on the root) on the surface of the tongue.

Texture of Fur
苔质

1. Thickness of Fur 苔的薄厚

Thin fur refers to a tongue coating through which the underlying tongue surface is faintly visible. Thick fur is a tongue coating through which the underlying tongue surface is not visible.

Thin tongue fur is usually seen in a normal person, or at the primary stage of externally contracted disease, or when a pathogenic factor is superficial and the disease is mild. Thick tongue fur is a sign of exuberance of both pathogenic factors and stomach qi, usually observed in the patterns of phlegm-dampness, food accumulation, and interior heat.*

During the course of a disease, change of the tongue fur from thin to thick indicates pathogenic qi becoming exuberant, development of pathogenic factors from the exterior to the interior, or progress of a pathological condition from mild to severe. On the contrary, change of the tongue fur from thick to thin suggests that healthy qi is getting stronger and the pathogen is getting weaker, development of pathogenic factors from interior to exterior, or progress of the pathological condition from severity to mildness.

2. Moist, Slippery, Dry, and Dry and Cracked Fur 润苔、滑苔、燥苔和燥裂苔

Moist fur refers to a moderately moistened tongue coating. Slippery fur refers to a moist tongue coating with excessive fluid, which feels slippery. Dry fur refers to a tongue coating that looks dry and feels dry to touch. And dry and cracked fur is a tongue coating that lacks moisture and develops cracks.

Moist and dry fur mainly reflect exuberance or deficiency of body fluid and its distribution. Moist fur usually indicates sufficient body fluid, mostly seen in healthy people. If moist fur is seen during the course of a disease, it indicates that the body fluid is not impaired. Dry fur usually indicates fluid deficiency, observed in exuberant heat, profuse sweating, severe vomiting, or over dosing hot natured drugs.

Slippery tongue fur usually indicates dampness and phlegm-retained fluid as excessive fluid leads to slippery tongue fur.

During the course of a disease, the change of the tongue fur from moisture to dryness indicates consumption of body fluid and severity of heat, while the change of tongue fur from dryness to moisture suggests decrease of pathogenic heat and gradual restoration of body fluid.

3. Slimy*, Sticky Slimy*and Curdy*Fur 腻苔、黏腻苔和腐苔

Slimy fur refers to a dense, turbid, slimy tongue coating, sticking on the tongue, hard to wipe off, also known as greasy fur. Sticky slimy fur is a dense, turbid, slimy tongue coating, covered with a layer of thick turbid mucus. Curdy fur refers to a tongue coating consisting of coarse granules like bean dregs*, easy to wipe off.

Slimy fur usually arises when dampness-turbidity accumulates in the body obstructing yang qi, and can be seen in the patterns of phlegm, dampness, retained fluid, and food accumulation. Thick and sticky slimy fur associated with a sweet taste in the mouth usually indicates dampness-heat in the spleen and stomach.

Curdy fur is usually caused by food accumulation in the stomach and phlegm-dampness in the body but with heat. Purulent and curdy fur indicates pathogenic toxin binding internally. The change from curdy fur to thin white fur during a disease indicates healthy qi is winning and the patient is recovering. But if new fur fails to be produced after the curdy fur's disappearance, then it indicates stomach qi deficiency.

4. Peeling Fur 剥苔

Peeling fur refers to complete or partial peeling of the tongue coating. Based on which region on the tongue has fur peeling, various names are given. Peeling of the forward part of the tongue fur is called anterior peeling fur*; peeling of the center of the tongue fur is called center peeling fur; peeling of the root part of the tongue fur is called root peeling fur; small coating only remaining in the center of the tongue is called chicken heart tongue; and very little tongue fur remaining at several places is called flower peeling fur. A completely smooth tongue, free of coating and like a mirror, is called mirror tongue*. A tongue with irregular shedding* of the coating with clear separation between the shed and unshed areas, looking like a map, is named geographical tongue*. Peeling of the tongue coating which leaves an unsmooth tongue surface as if covered with regeneration of coating granules* is called exfoliated fur*.

Peeling fur indicates stomach qi deficiency, or stomach yin debilitation, or dual deficiency of qi and blood, which is also a sign of whole body deficiency, because all these conditions can make the stomach fail to generate tongue fur properly.

Red tongue with peeling fur usually indicates yin deficiency. Pale tongue with peeling fur indicates blood deficiency or dual deficiency of qi and blood. Crimson and mirror tongue indicate stomach yin depletion, a severe yin deficiency condition. Pale and mirror tongue indicates severe deficiency of blood and body yang. If the flower fur or the fur on geographical tongue is slimy, it indicates that phlegm is not resolved, but healthy qi is impaired and the disease is complicated.

During the course of a disease, if the tongue fur changes from completion to peeling, it indicates insufficiency of stomach qi or /and stomach yin and gradual decline of healthy qi. If pale and thin fur appears after fur peeling, it indicates decline of pathogenic qi and gradual restoration of stomach qi.

Fur Color
苔色

Fur color refers to the color of the tongue coating, white, yellow, gray or black, and in rare cases, green. And they may appear alone or combined.

White fur usually indicates healthy, or exterior pattern, dampness pattern, and even cold pattern. White thin fur is normal tongue fur and is mostly seen in healthy people. Pale red tongue with thin white fur* is usually observed in healthy people or wind-cold exterior pattern. In a morbid condition, white thin fur is usually seen at the early stage of exterior pattern, cold pattern, mild internal pattern, or deficiency internal cold. Thin, white and moist tongue fur indicates wind-cold external contraction. White, thin, and dry fur indicates wind-heat external contraction. Thin, white and slippery fur indicates cold-dampness external contraction. Thin and white fur can also be seen in deficiency cold pattern.

The formation of white, thick and slimy fur is usually due to internal retention of dampness-turbidity*, phlegm-retained fluid formation, or food accumulation not transformed into heat yet. White, thick, slimy and slippery fur indicates dampness-turbidity and phlegm-retained fluid. White, thick and dry fur indicates accumulation of phlegm-dampness-heat in the body.

Yellow fur usually indicates interior pattern and heat pattern. During the course of a disease, the change of fur from white to yellow suggests that the pathogenic factors have transformed into heat. Generally speaking, the yellower the tongue fur is, the more severe the pathogenic factor it indicates. Light-yellow fur indicates mild heat, deep-yellow fur signifies severe heat and dryness yellow fur suggests extreme heat. Red tongue with thin, yellow and dry fur* is usually observed in internal heat pattern or a pattern in which fluid has been damaged. Yellow fur usually appears simultaneously* with red and crimson tongue, because they all suggest heat pattern.

Thin and yellow fur indicates mild pathogenic heat, usually seen in wind-heat exterior pattern, or inward invasion of heat transformed from wind-cold, or mild interior heat pattern. Alternate yellow and white fur on the tongue suggests that the pathogenic factor is being transmitted from the exterior to the interior or cold is transforming into heat. Yellow and slimy fur usually indicates accumulation of dampness-heat, or phlegm-retained fluid transforming into heat, or food retention being fermented by heat. Yellow and dry fur is often caused by heat damaging body fluid.

Black fur indicates either excessive cold or extreme heat in the interior, and gray fur has similar clinical significance as black fur, and they almost always appear at the same time; therefore, most of the time they are called gray-black fur. Moreover, gray-black fur indicates a severe pattern regardless of cold or heat. Moist, gray and black fur indicates excessive cold, while dry, gray and black fur indicates extreme heat, the deeper fur color of gray-black, the more severe the pathological condition is. Gray-black fur in cold pattern usually develops from white fur; therefore, gray-black fur must be moist in cold exuberance or yang deficiency pattern. Gray-black fur in heat pattern usually comes from dryness and yellow fur; therefore, gray-black fur must be dry in heat pattern. However, gray-black fur can be also seen in heavy smokers.

Greenish fur is usually observed in extreme heat pattern, such as pestilence, or dampness-warmth.