bubble_chart Concept

The coating on the tongue appearing white is called "tongue coating white." The character "苔" was also written as "胎" in ancient times.

The "Guide to Tongue Diagnosis: White Coating Diagnostic Method" states: "...the tongue base is light red, the tongue coating is slightly white,...neither too dry nor too moist, neither slippery nor dry, this is the coating of a healthy tongue...." That is, a normal person's tongue texture is light red, and the tongue coating is slightly white, which is different from pathological white coating and should be distinguished. Additionally, if the tongue coating is white and greasy, refer to the entry on "tongue coating white and greasy."

bubble_chart Pattern Analysis

1. External Contractionwind-cold︰The tongue coating is thin and white, with symptoms such as aversion to cold or aversion to wind, headache and painful stiff nape, fever, absence of sweating, body pain, and a floating and tight pulse. The wind-cold pathogen invades the exterior of the body, entering through the skin and hair, and affects the taiyang Bladder Channel. Cold, being a yin pathogen, tends to damage yang qi. Hence, the *Guide to Tongue Differentiation* states: "A tongue without coating and moist, or with slight thin white coating, indicates wind-cold; the external symptoms must include aversion to cold and fever." The key points for diagnosis are: mild fever with severe aversion to cold, absence of sweating, absence of thirst, white and moist tongue coating, normal tongue texture, headache and body pain, and a floating pulse. The treatment principle is to release the exterior with pungent-warm herbs, and the prescribed formula is Ephedra Decoction.
2. Cold-dampness Attacking the Exterior︰The tongue coating is white and slippery, with aversion to cold accompanied by fever, absence of sweating, headache and heaviness of the head, heavy pain in the lumbar spine, soreness and pain in the limbs, or generalized pain all over the body that prevents turning or moving, and a tight pulse. The disease cause is exposure to cold during early morning travel, or long-distance travel with sweating followed by exposure to cold rain, leading to external contraction of cold-dampness, Xieke affecting the muscular exterior. Since the pathogen has not yet transmitted inward, the tongue coating is white and slippery. The *Guide to Tongue Differentiation* states: "Cold-dampness is fundamentally a yin pathogen; white indicates a cold nature, hence a slippery white coating signifies wind-cold combined with dampness." The nature of cold-dampness is heavy, turbid, and stagnant, hence headache and heaviness of the head, heavy pain in the lumbar spine, or generalized pain all over the body, with a wiry and tight pulse. Yang qi is constrained and unable to disperse, resulting in aversion to cold with fever and absence of sweating on the muscular exterior. This pattern resembles the white tongue coating seen in the pattern of common cold due to wind-cold, but in cases of wind-cold invading the exterior, the tongue coating is white and moist, accompanied by symptoms of the wind-cold common cold pattern. In contrast, when cold-dampness attacks the exterior, the tongue coating is white and slippery, accompanied by symptoms of dampness stagnating in the muscular exterior. Treatment should focus on dispersing wind and resolving dampness, using the formula Notopterygium Overcoming Dampness Decoction.
3. Spleen Yang Deficiency︰The tongue coating is white, glossy with little moisture, distributed like scattered snowflakes on the tongue. Its color is whiter than ordinary white coating, commonly referred to as "snowflake fur." It is also accompanied by a dull complexion, cold pain in the abdomen that prefers warmth and pressure, intermittent relief of abdominal distension and fullness, poor appetite, loose stools, clear urine, cold limbs, fatigue and lack of strength, shortness of breath and reluctance to speak, and a slow or weak pulse. This syndrome arises from prolonged deficiency of spleen yang, repeated vomiting or diarrhea severely damaging middle qi, or excessive consumption of cold drinks leading to cold in the middle, resulting in gradual decline of spleen yang. Internal cold congeals and obstructs the middle energizer, impairing both the transformation of water-dampness and the distribution of body fluids, leading to a white, dry, and glossy tongue coating resembling snowflakes. *The Guide to Tongue Differentiation* states: "When the tongue develops a white coating like snowflakes, this is commonly called snowflake fur, indicating cold and obstruction of the spleen." The key diagnostic features include not only the white coating but also cold abdominal pain, abdominal distension and fullness that prefers warmth, cold limbs, and signs of spleen dysfunction and internal cold deficiency. Treatment should focus on warming the middle and strengthening the spleen, using sweet and warm herbs to support yang. The recommended formula is Aconite Middle-Regulating Decoction with modifications.

A white coating on the tongue generally indicates a cold pattern. The "Essential Theory of Cold Damage Diseases" states: "All fur coatings, if white in color, indicate cold; the whiter it is, the more severe the cold." Cold can be divided into exterior cold and interior cold. Exterior cold often presents with a thin white coating; interior cold shows a slightly thicker white coating; if accompanied by dampness, the coating becomes white and greasy; if caused by spleen yang deficiency, the coating is white and clean, with little moisture and a shiny appearance, resembling snowflakes. Based on clinical manifestations, it is relatively easy to differentiate. Generally, a thin white coating indicates a mild condition, a thick white coating indicates severe interior cold, and a snowflake-like coating is a critical sign of spleen qi exhaustion. As stated in the "Tongue Diagnosis of Cold Damage Diseases": "A white coating can also indicate fatal conditions and should not be overlooked."

bubble_chart Documentation

1. 《Cold-Damage Disease Tongue Mirror: General Discussion on White Coated Tongue》: "A dry and thick white-coated tongue, after four or five days of illness without sweating, pathogenic heat gradually deepens, with slight thirst, excessive consumption of cold and raw foods, accumulation in the chest, leading to heat in the nutrient aspect and cold in the stomach, thus causing fever and dysphoria, reversal cold of the limbs, and a white, dry, thick coating with white debris all over the mouth. It is appropriate to use Gegen Tang with Dried Ginger."
2. 《Four Examinations: Essentials of Inspection》: "If the tongue shows a white coating like the color of cooked food, thickly covering the tongue, it is due to excessive consumption of cold drinks. If the pulse cannot be felt, it is fatal. Cold-Extremities Decoction can be used to rescue."
3. 《Wenre Jingwei》. Ye Xiang-yan's External Contraction Warm Heat Chapter: "Again, if the tongue coating is white, thick, and dry, it indicates injury to the stomach's dryness qi. Add Liquorice Root to the moistening medicine, aiming to retain the fluid by sweetness. ... If the coating is white, dry, and thin, it indicates injury to the lung's fluid. Add Ophiopogon Tuber, flower dew, Reed Rhizome juice, and other light and clear substances, with emetic therapy being the superior method. If the white coating has a crimson base, it indicates heat retention due to the blockage of dampness. First, drain the dampness and let the heat out, preventing it from drying out. Do not worry, as it will become moist again when the heat is released from the inside to the outside."
4. 《Guide to Tongue Differentiation: Differentiating Tongue Colors》: "A full white tongue coating, dry, sticky, and scorched, which cannot be scraped off or not completely, indicates interior heat consolidation. ... If the tongue and the entire mouth produce a white coating like mold or mildewed spots, it indicates decay of the stomach body, often fatal."