Library

At the initial stage of Taiyang exterior syndrome, the tongue usually has no coating and is moist. If there is a coating, it is slightly white and thin, or even pale white. Only in those who are prone to phlegm-dampness is the coating mostly white and slippery. The tongue body color is light red. In individuals with a constitution prone to blood heat, although the coating may be slightly white, the tongue body color tends to be red. If the pathogen transmits to its associated fu organ (the Bladder), causing water accumulation in the bladder, the coating is mostly pure white and thick, but not dry or rough. If there is heat accumulation in the bladder, the coating is mostly white mixed with slight yellow, thin and slippery.

[Commentary by Xiu] The Qi transformation of the Taiyang channel governs water metabolism and its nature is originally cold. Cold is a yin pathogen, and white represents a cool image; therefore, the coating color is mostly white. White and moist, or white and thin coatings, represent the original manifestation of this condition. A white and slippery coating indicates wind-cold combined with dampness; a white, slippery, and greasy coating indicates wind-cold combined with dampness and phlegm. Whether the coating is thin or thick depends on the amount of phlegm-dampness in the body. Only when the coating is pale white, white, tender, and slippery does it indicate a constitution of deficiency-cold.

[Commentary by Lian] A white and thin coating indeed indicates cold pathogen at the exterior. However, it must be a floating, slippery, and thin white coating that regrows after scraping to confirm cold pathogen affecting the Taiyang channel exterior. If the entire tongue is covered with a white coating that is floating, swollen, and greasy, gradually accumulating and becoming dry, slightly thick, and difficult to scrape off, this indicates that the cold pathogen is transforming into fire. If at onset the coating is white, thin, and dry with prickles, this indicates warm disease triggered by cold invasion, where lung fluids have been damaged. If the inner layer of the coating is thin and sticky, this indicates damp pathogen residing in the qi level. Thus, although the coating color is thin and white, one case indicates cold pathogen at the exterior, another indicates qi stagnation, and another indicates damage to lung fluids.

The Shaoyang channel governs the half-exterior and half-interior. When the disease leans towards the half-exterior, the tongue mostly shows a white and slippery coating, or white coating only at the tip, or on one side, or on both sides. When the disease leans towards the half-interior, the tongue is mostly red with a white coating, interspersed with other colors. For example, white tip with red center, white edges with red center, red tip with white center, white tip with black root, or white tip with grey root. If the white coating is abundant and slippery, while yellow/grey coatings are scarce, the half-exterior syndrome predominates. If the red tongue body is abundant with little white coating, or mixed with yellow/grey colors, the half-interior syndrome predominates. If the edges are white, slippery, and moist, despite a yellow/black center, it still belongs to the half-exterior/half-interior syndrome. Only when the white coating is coarse like accumulated powder, with red or purple edges, does it indicate warm epidemic pathogen latent in the Mo Yuan (membrane source). A white coating resembling salt frost indicates turbid filth latent in the Mo Yuan.

[Commentary by Xiu] The Hand Shaoyang channel externally governs the interstices (Cou Li) and internally governs the San Jiao and Mo Yuan. Therefore, *Shanghan Lun* states: "If there is cold in the chest and heat in the Dantian, and a white coating on the tongue, do not use purgatives." Roughly, the chest refers to the Upper Jiao, and the Dantian refers to the Lower Jiao. If the coating is white, slippery, and thick, it indicates cold fluid accumulation above the diaphragm and latent heat accumulation in the Lower Jiao. One should only employ bitter-pungent harmonization methods, not purely purge the interior. Thus, a white tip with yellow/black root, or yellow center, or half-grey/half-white coating, all belong to half-exterior/half-interior syndromes. Observing the quantity of white: if white is abundant, exterior pathogen remains significant, so harmonization combined with exterior-resolving is appropriate. Zhang’s Chaihu Guijiang Tang and Yu’s Chaihu Zhijie Tang facilitate the free flow of the Upper Jiao, descent of fluids, and harmony of Stomach Qi, leading to resolution through spontaneous sweating. If yellow/black/grey colors predominate, or if prickles, black spots, or dry cracks appear, even if the coating is white, indicating that although exterior pathogen is not fully resolved, interior heat has consolidated, urgent harmonization combined with purgation is required. Zhang’s Da Chaihu Tang and Yu’s Chaihu Xiantong Tang are designed for this purpose, allowing pathogen to exit from below. If the Foot Shaoyang channel is solely governed by Gallbladder fire, the tongue is mostly bright red; even if white mixes with red, prickles often appear. Urgent harmonization combined with clearing is needed. Yu’s Chaihu Baitou Tang and Yu’s Haoqin Qingdan Tang clear ministerial fire and drain Gallbladder heat.

[Commentary by Lian] Whenever cold pathogen leaves the Taiyang exterior but has not entered the Yangming interior, it resides in the Hand Shaoyang channel, hence termed half-exterior/half-interior. Thus, whenever a white coating is floating, slippery, greasy, and swollen, and scraping yields inconsistent results, it signifies cold pathogen transmitted to the Hand Shaoyang channel, occupying the half-exterior/half-interior sector. Yu’s Chaihu Zhijie Tang is suitable for this syndrome. If the tongue coating is coarse like accumulated powder, rough to touch, and cannot be completely scraped off, it indicates damp-heat has consolidated in the Mo Yuan of the chest, diaphragm, and abdominal membranes. "Yuan" refers to the hollow spaces within the membranes, connecting externally to muscles and internally near the Stomach, serving as the boundary between interior and exterior, effectively the half-exterior/half-interior of the whole body. Hence, external pathogens enter inward via the Mo Yuan, and internal pathogens exit outward via the Mo Yuan. Wu Youke created Daren Yin with profound insight. However, Zhimu directly clears Yangming heat, and Baishao drains Jueyin fire, which does not perfectly align with the Shaoyang channel. Yu removed Zhimu and Baishao, adding Zhike, Jiegeng, Chaihu, and Qingpi, making the formula more precise. Zhike and Jiegeng are lightly bitter and pungent, gently venting the Upper Jiao; Houpo and Caoguo warm and unblock the Middle Jiao; Qingpi and Binglang reach directly to the Lower Jiao; Chaihu reaches the membrane to resolve the half-exterior; Huangqin clears fire to drain the half-interior; Gancao harmonizes the herbs. This is an excellent formula for early-stage damp-warmth and seasonal epidemics, also effective for common damp-heat resembling malaria. However, in cases where latent pathogen resides in the Ying level and emerges from Shaoyin to Shaoyang, such as Spring Warmth, the mild fire transforms into vigorous fire. Tongues appearing light red, tender red, or white-mixed-with-red represent mild warm disease. Sudden onset of pure bright red, even with prickles, indicates blazing Gallbladder fire and heat differentiating in the Ying level, representing severe warm disease.

Yangming resides in the interior; a true yellow coating mostly indicates interior excess. Yellow-white mixture suggests pathogen still in the channels; slight yellow and thin indicates shallow pathogen with middle deficiency; yellow and rough/rough indicates pathogen entered the Fu organs; light yellow and thin/greasy indicates slight Stomach heat; deep yellow and thick/greasy indicates excessive Stomach heat; old yellow or scorched yellow, possibly mixed with grey/black or prickles, indicates extreme Stomach heat. Yellow and slippery indicates phlegm-fire; yellow and greasy indicates damp-heat; yellow and dirty/greasy indicates damp-heat with food stagnation; yellow with black spots indicates warm toxin mixed with filth; yellow, thick, but not dry with blue-purple tongue body indicates retention of cold wine or cold food. Yellow and dull/dark indicates retention of phlegm-fluid or cold-stasis.

[Commentary by Xiu] A yellow and slippery coating indicates heat has not consolidated; purgation should not be used immediately. A yellow and dry coating indicates intense heat; drastic purgation is indicated. Yellow with prickles and black spots indicates extreme heat. Yellow with petal-like cracks indicates dried stomach fluids; the indication for purgation is especially urgent. There are cases where the root is yellow, thick, and greasy, the tip is white, the center is not very dry nor slippery, but the tongue is short and cannot extend; this indicates stubborn food stagnation郁伏 (retained) in the Stomach. There are also cases where the coating is yellow and thick, even cracked, but the tongue body is blue-purple and not dry; this indicates cold combined with food stagnation. Although various yellow coatings belong to Stomach heat, one must distinguish urgency and severity for purgation, and consider adjuvant warming, heating, resolving, or tonifying methods. Clinicians must differentiate carefully.

[Commentary by Lian] White coating governs exterior and also half-exterior/half-interior. Although yellow coating specifically governs interior, it can present with white. In clinical practice, for every point of white on the coating, there is a corresponding point of exterior involvement. Thus, yellow-white mixture, or grey-white with slight yellow, should not be lightly treated with Sanhuang (Coptis, Scutellaria, Phellodendron) alone for bitter cold drainage. Often, exterior pathogen is unresolved while interior heat has consolidated, or there is qi-level stagnant heat, or dampness suppressing heat. Despite chest/epigastric fullness, one should use opening/draining methods to ventilate qi mechanism and reach the exterior. Even thin, slippery yellow coating indicates formless damp-heat with deficiency signs, requiring aromatic/light draining methods to clear heat and vent exterior. Only when the coating is pure yellow without white does the pathogen leave the exterior and enter the interior. Old, deep, or scorched yellow indicates pathogen leaving the channels and entering the Fu organs. However, yellow varies and requires detailed differentiation. Liu Jiren’s new tongue diagnosis method clarifies this: (1) True yellow coating is the normal color of Stomach heat, indicating Shanghan transmitted to Yangming interior, or early transmission in warm disease. For damp-warmth/warm-heat, medication should be differentiated by pulse (slippery/rapid vs. choppy/weak). (2) Tender yellow coating, changing from white to tender yellow, indicates initial rise of Stomach turbidity and awakening of Stomach Yang. (3) Old yellow coating indicates盛 (excess) of Stomach-Yang. If thick and rotting/piling up, it indicates rising of dietary turbidity, beginning of damp-warmth transforming to heat, and burning of fluids by warm-heat. (4) Tooth-yellow coating indicates initial rise of Stomach turbidity. Tooth-yellow without pores is called greasy coating, indicating phlegm in Middle Jiao. (5) Water-yellow coating, resembling chicken egg yolk mixed with white, is yellow and slippery, the correct sign for phlegm-fluid retention in damp-warmth. It may also occur in warm-heat with fluid retention, or after mistakingly taking drying drugs for heat entering Stomach. Differentiate by pulse and symptoms. (6) Yellow putrid coating, resembling fried bean curd residue piled up, indicates purgation is needed. If central vertical cracks exist, it indicates qi deficiency; do not purge, instead tonify qi due to insufficient transportation. (7) Yellow coating like wax paste indicates damp-warmth with phlegm-stagnation; thus no pores and greasy. (8) Yellow coating like tiger stripes indicates simultaneous burning of qi and blood. (9) Yellow coating like millet grains, distinct particles, indicates hyperactive Stomach Yang. (10) Yellow coating like fried Zhiqiao (Aurantii Fructus), indicates extreme Stomach Yang hyperactivity and yin deficiency. Stomach juice is dried; coating resembles fried Zhiqiao, withered and not moist. (11) Yellow coating like agarwood, indicates extreme Stomach heat and impending exhaustion of Stomach fluids. (12) Yellow mixed with grey coating indicates Wind-Warmth combined with dampness, depressed Yang; thus coating lacks normal color; first resolve qi and open depression. (13) Yellow-black mixed like scorched cake, prickly to touch, dull to look, indicates scorching of Stomach fluids, dry mouth/tongue. However, if Yang is blocked by Yin pathogen and cannot vaporize to generate fluids, diagnose by pulse. Slippery, forceful pulse indicates fire burning fluids; choppy, weak pulse indicates phlegm-fluid/stasis blocking Yang, preventing fluid generation.

Taiyin governs dampness; tongue mostly shows grey coating, even black. Grey and slippery/greasy indicates heavy dampness with cold; grey and pale white indicates severe Spleen Yang deficiency; grey and rough/greasy indicates damp stagnation with heat consolidation; grey and dry indicates impending Spleen Yin exhaustion. Grey with greasy coating and rough/dry/scorched tongue body that cannot be cleanly scraped indicates heat syndrome where dampness exhausts and transforms to dryness. Grey-black greasy coating with tender/slipping/moist tongue body that does not change color when washed indicates cold syndrome with heavy dampness and Yin involvement. Whenever coating is grey or black, or mixed, the condition is often critical; do not underestimate it.

[Commentary by Xiu] Grey resembles ash, black resembles ink; although both are damp-turbid yin pathogens, once coating forms, excess-heat is more common than deficiency-cold. Except for grey tongue with moisture, no thick coating, no color change, pale black tongue with white mixed, and slippery tongue body (indicating deficiency-cold), otherwise, yellow turning grey/black, regardless of tip, center, or root being grey/black, pure grey, or pure black, if tongue body is dry/rough, with prickles/cracks, petal-like formations, or halos, these are heat syndromes of Shanghan transmitting through channels, or fire syndromes of warm-heat damaging zang organs. Regardless of location (root, center, tip), urgent purgation is needed to preserve fluids, supplemented by resolving or tonifying methods as clinically appropriate. Only in summer heatstroke is the coating mostly grey/black, or grey slippery/thick, or black slippery/thick, indicating damp-phlegm郁热 (depressed heat); this should not be discussed together with channel-transmission syndromes. If repeated purgation fails to remove grey/black, or repeated clearing increases it, and the tongue is round/large/fat/tender, or coating is not very dry but heart is black/grey with little coating debris, these are deficiency syndromes of Yin injury. Urgently tonify water and nourish Yin. Neither Xiaoshi/Mangxia (Mirabilite/Gypsum) nor Jiang/Fu (Ginger/Aconite) should be used.

Shaoyin governs heat, harboring Minister Fire within, mostly involving blood deficiency; tongue color is mostly red. Light red/shallow red is the natural color of blood deficiency; deep red/purple-red indicates extreme blood heat; bright red/burning red indicates severe yin deficiency with fire; tender red/dry red indicates yin deficiency with fluid exhaustion. Red turning crimson (Jiang) indicates extreme blood deficiency. Crimson and moist indicates deficient heat; crimson and dry indicates excess heat; crimson with prickles indicates fierce blood-fire; crimson with dry cracks indicates yin damage and fluid exhaustion.

[Commentary by Xiu] The Heart opens into the tongue; thus red tongue is the normal color of the Heart, and crimson tongue is the true organ color of the Heart. Appearance of true organ pulse indicates critical illness; appearance of true organ color indicates even more critical illness. Therefore, regardless of pulse/symptoms, seeing a crimson tongue is generally inauspicious. Heart channel blood heat results in true red tongue, color like red flower; heavy heat toxin results in deep red tongue, color like red satin; particularly heavy heat toxin results in delicate red tongue, color like peach blossom; heavy heat toxin with blood stasis results in purple-red tongue, color like rouge. These are all red tongues. Red tip indicates Heart fire flaming upward; red root indicates blood heat scorching downward. Completely red without coating, or seemingly coated and sticky, indicates blood heat mixed with filth. Red stars, spots, cracks, fragments indicate extreme heat toxin. Red mixed with white coating indicates exogenous cold wrapping fire; red mixed with black coating indicates pathogenic heat transmitting to Kidney; red with two grey strips indicates damp-heat mixed with cold food; red with white dots indicates Heart heat burning Lung; red mixed with yellow/black and prickles indicates Heart heat transferring to Stomach Fu. Pale red indicates blood deficiency; pale red without coating, slightly red mixed with yellow/white coating, indicates qi failing to transform fluids; pale red with cyan tint indicates blood-level deficiency-cold. Only red that is tender, like red persimmon, looking moist but feeling dry upon touch, is a crimson tongue, mostly caused by excessive sweating/purging leading to blood exhaustion; illness is often untreatable. Zhang Zhongjing’s Zhi Gancao Tang is often ineffective in saving such cases.

Jueyin Qi transformation governs wind; wind transforms from fire, tongue mostly scorched purple. There is also cold transformation, where tongue is mostly cyan and slippery. Seeing cyan/purple tongue indicates ominous prognosis. Deep purple with red indicates Liver heat and collateral stasis, or yang-heat wine toxicity; pale purple with cyan indicates cold invading Liver/Kidney, or cold injury after drinking alcohol.

[Commentary by Xiu] Purple tongue color always indicates Liver collateral stasis. Stasis due to heat results in deep purple/red tongue, either dry or scorched; stasis due to cold results in pale purple/cyan tongue, either slippery or dark. Other causes include long-term phlegm-stasis stagnation or chronic consumption of cold wine, often presenting purple tongue. Only purple, dry, and dull, resembling cooked pig liver, indicates destruction of Liver/Kidney and appearance of true organ color; death is certain.

[Commentary by Lian] The Liver contains many collaterals and stores blood; blood color is cyan/purple. Any bluish veins visible on skin are collaterals. Thus, cyan/purple tongue is indeed the normal color of Jueyin Liver disease. However, the Hand Jueyin Pericardium channel still presents red tongue.