bubble_chart Concept

A tongue coating that appears gray with black is referred to as "gray-black tongue coating" or "gray-black tongue fur."

Strictly speaking, the color and associated illnesses of gray tongue coating and black tongue coating are not entirely the same. When the tongue coating color is a light black, it is considered gray; when the tongue coating color is a deep gray, it gradually turns black. Gray fur indicates a slightly milder illness, while black fur indicates a more severe illness. However, in terms of the development and outcome of the condition, the two are closely related. Therefore, they are discussed together.

A gray-black tongue coating generally indicates a more severe condition, and clinical differentiation should be based on the moisture or dryness of the tongue surface and the overall symptoms.

bubble_chart Pattern Analysis

1. Spleen Yang Deficiency︰The tongue coating is grayish-black, thin, and moist; the complexion is pale yellow; there is poor appetite, cold pain in the abdomen, abdominal distension and fullness, which are relieved by warmth; no thirst, preference for hot drinks; loose stools or diarrhea with undigested food; cold limbs; a frail and cold appearance; and a deep, slow pulse. This is often caused by prolonged deficiency of spleen qi, where qi impairment affects yang, or by direct invasion of cold pathogens, improper treatment, excessive consumption of raw or cold foods, injury to spleen yang, or failure of middle yang to rise, leading to internal exuberance of pudendal coldness. As stated in *The Guide to Tongue Differentiation*: "If the tongue coating is grayish-black and slippery, this indicates cold water restricting earth, with taiyin cold in the middle." The grayish-black tongue coating due to internal obstruction of phlegm-fluid retention arises from the failure of spleen yang to rise, preventing body fluids from being properly distributed and circulated. This leads to the accumulation of dampness, retention of fluids, and congealment into phlegm, with cold-phlegm-dampness stagnating in the stomach and intestines, resulting in exuberant cold-dampness. The key points for differentiation are as follows: In the former case, the stomach lacks turbid pathogens, so the tongue coating is grayish-black, thin, and moist, accompanied by signs of spleen yang deficiency and yang deficiency with cold in the middle, such as cold pain in the abdomen, absence of thirst, cold limbs, anorexia with loose stools, and a deep, slow pulse. If there is dysfunction of the spleen in transportation, leading to failure in ascending and descending, the stomach fails to descend turbidity, causing vomiting, while the spleen fails to ascend the clear, resulting in spontaneous diarrhea. For such patients, treatment should focus on warming the middle and dissipating cold. The recommended formula is Aconite Middle-Regulating Decoction.
2. Internal Retention of Water and Fluid︰The tongue coating is gray-black and slippery with moisture, or gray-black and greasy, accompanied by dizziness and blurred vision, abdominal distension and fullness, splashing sounds in the epigastric region, vomiting of clear water and phlegm-drool, thirst without desire to drink, borborygmus and loose stools, or a body that was originally robust but now emaciated, heaviness and weakness of the body, fatigue and exhaustion. In severe cases, there may be rigidity and numbness in the lower abdomen, throbbing below the navel, scanty urine, or symptoms such as cough, palpitations, and shortness of breath. The pulse is wiry and slippery. The presence of phlegm-fluid retention internally in the stomach leads to a gray-black, thick, and moist tongue coating, along with symptoms of phlegm-fluid retention and damp-turbidity obstructing the stomach and intestines, such as distension and fullness in the chest and hypochondrium, splashing sounds in the epigastric region, thirst without desire to drink, vomiting of clear water and phlegm-drool, borborygmus and loose stools, and a wiry-slippery pulse. The treatment principle is to warm yang and resolve retained fluid. The recommended formula is Poria, Cinnamon Twig, Bighead Atractylodes and Licorice Decoction or similar prescriptions.
3. Dampness-heat︰The tongue coating is gray-black, thick, greasy, and sticky, concealing fever, with obvious heat manifestations in the afternoon, or alternating chills and fever, bitter taste in the mouth, dry lips, a pale yellow or dull complexion, chest and gastric stuffiness, abdominal distension and fullness, loose stools with incomplete evacuation, scanty and yellow urine, fatigue and heaviness, soreness and discomfort in the limbs, and a deep, slippery pulse. This is mostly caused by dysfunction of the spleen in transportation, internal retention of water-dampness, prolonged stagnation transforming into heat, steaming of dampness-heat, and obstruction of filthy turbidity in the middle energizer. The treatment should focus on dispersing with acrid herbs, aromatic transformation, resolving dampness, and clearing heat. The recommended formula is Three-Kernel Decoction, or alternatively, Coptis RhizomeGallbladder-Warming Decoction.
4. Heat Scorching Kidney Yin︰The tongue coating is gray-black, dry, and prickly, accompanied by restlessness and insomnia, feverish body and flushed face, dry throat, and thirst. Symptoms may also include dizziness, tinnitus, deafness, palpitations, forgetfulness, soreness and weakness in the lower back and knees, dry stool, scanty dark urine, and a thin, rapid pulse. This condition arises from constitutional yin deficiency, where cold pathogens invade the Shaoyin and transform into heat, or from warm disease pathogenic heat penetrating deeply into the Shaoyin, exacerbating exuberance of heart fire above and depleting kidney water below. As a result, kidney water fails to nourish the heart, leading to increasingly intense heart fire, which further depletes kidney water, ultimately resulting in a pattern of true yin exhaustion and rampant fire. Both scenarios manifest as excess patterns, but their disease causes and mechanisms differ, leading to distinct clinical presentations: - In cases of internal dampness-heat accumulation, the tongue coating is gray-black, thick, greasy, and sticky, accompanied by chest and gastric stuffiness, abdominal distension and fullness, nausea, and other symptoms of dampness-heat turbidity obstructing the middle burner, disrupting spleen and stomach functions. Alternatively, hidden fever, bitter taste in the mouth, dry lips, fatigue, sore limbs, and a deep, slippery pulse may indicate heat steaming internally with dampness encumbering spleen yang. - In cases of heat scorching kidney yin, the tongue coating is gray-black, dry, and prickly, with a red tongue texture, along with symptoms such as inner heat and restlessness, insomnia, feverish body and flushed face, consumptive thirst, and a thin, rapid pulse, reflecting kidney yin deficiency and exuberance of heart fire. Treatment should focus on enriching yin, tonifying the kidneys, and clearing heart fire. Recommended formulas include Coptis and Ass Hide Glue Decoction and Modified Pulse-Restoring Decoction.

A black coating is an interior pattern, with its primary diseases differentiated into cold, heat, phlegm, and dampness, often seen in severe stages of illness. For instance, a thin gray-black tongue coating indicates spleen yang deficiency; a dry, gray-black tongue coating with prickles suggests heat scorching kidney yin; a gray-black, moist tongue coating points to internal obstruction by phlegm-dampness; and a thick, greasy, sticky gray-black tongue coating indicates internal accumulation of dampness-heat or damp-phlegm with stagnant heat. In cold-damage disease, a gray-black and moist tongue coating is commonly seen in the three yin channel diseases, often indicating deficiency of yang with exuberance of yin, a sign of water overcoming fire, which is an adverse condition; whereas a gray-black and dry tongue coating is often seen in the three yang channel diseases, typically indicating extreme fire resembling water, a condition that can be treated with purgation. Distinguishing between these two conditions makes it easier to identify other syndromes.

bubble_chart Documentation

1. 《Cold-Damage Disease Tongue Mirror: General Discussion on Gray Tongue》: "Gray-black dry thorn tongue: In the gray-black tongue, there are also dry thorns, which can indicate dry throat, dry mouth, and panting fullness. This is due to pathogenic heat accumulating in the Shaoyin, and purgation is necessary. However, one must wait for the passing of flatus before purgation can be performed. If purgation is done too early, it can cause difficulty in urination."
2. 《Four Examinations: Essentials of Inspection》: "If the tongue appears with heavy gray-black halos, this indicates that warm febrile disease heat toxin has spread to the three yin. Each time it spreads internally, the tongue gains another gray halo layer. The severity of the toxin causes heavy halos, which is a very dangerous condition. Immediate cooling of the diaphragm, dual resolution to remove toxins, and purgation with Chengqi Decoction are necessary. One halo is still mild, two halos are severe, and three halos are fatal. There are also cases with two or three horizontal lines, which are not different from heavy halos." "If the tongue edge is gray-black and the center is light purple, with frequent tongue biting and a sharp tongue tip, this indicates Shaoyin qi rebelling upwards, and no medicine can save it."
3. 《Guide to Tongue Differentiation: Diagnostic and Differentiation Methods for Gray Tongue》: "Quoting from 'Bian Zheng': Gray-black coating with dry fissured tongue, this is due to extreme heat in the viscera, caused by mistakenly eating hot foods or mistakenly taking warming and tonifying pungent and dry medicines, which scorch the true yin. Treatment should involve the extraordinary use of the Ten Complete Bitter Cold Rescue and Tonify Decoction, administered urgently and repeatedly until the gray-black color recedes and the fissures naturally smooth out, leading to immediate recovery."