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White coating is seen in the center of the tongue, with slightly yellow edges. Diarrhea (Xie) will certainly occur. It is suitable to take Jiedu Tang (Detoxification Decoction). If accompanied by aversion to cold (Ehan), Wuling San (Five-Ingredient Poria Pill) should be used.

[Commentary by Jie] White coating belongs to the Lung (Fei), and yellow coating belongs to the Stomach (Wei). Here, heat is blazing in the Stomach, while the pathogen remains in the Lung. If unresolved for a long time, the pathogenic heat from the Lung and Stomach transfers to the Large Intestine (Dachang), causing diarrhea. Therefore, Jiedu Tang is used to clear heat and detoxify. If the external syndrome presents with aversion to cold, it is diarrhea caused by cold-dampness (Han Shi), and the tongue coating must be moist. Thus, Wuling San is used to leach out dampness.

The tongue shows a slightly yellow color, indicating that the exterior syndrome (Biao Zheng) has not yet resolved. It is suitable to use Xiao Chaihu Tang (Minor Bupleurum Decoction) combined with Tianshui San (Heavenly Water Powder) as the main treatment. For cases where purgation is applicable, Da Chaihu Tang (Major Bupleurum Decoction) should be used to purge. This achieves simultaneous resolution of both interior and exterior. Clinicians should exercise careful judgment in application.

[Commentary by Jie] When the yellow coating is thin and slippery, it indicates that the pathogen has just entered the interior, the exterior syndrome has not yet resolved, and the heat has not yet damaged the body fluids (Jin Ye). One can still use herbs such as Chai Hu (Bupleuri Radix), Ge Gen (Puerariae Lobatae Radix), Huang Qin (Scutellariae Radix), and Lian Qiao (Forsythiae Fructus), or formulas containing Zhi Zi (Gardeniae Fructus), Dou Chi (Sojae Semen Praeparatum), Lian Qiao, and Bo He (Menthae Haplocalycis Herba) to lightly clear heat, thereby penetrating the exterior pathogen and reaching the muscle layer. If the yellow coating is thin but greasy/sticky, it represents a condition of damp-heat stagnation. Treatment should involve clearing heat while simultaneously using herbs that promote diuresis to drain dampness. Hence, Xiao Chaihu Tang combined with Tianshui San is used. However, since the pathogen is still between the exterior and interior (Ban Biao Ban Li), the use of Ren Shen (Ginseng Radix et Rhizoma) in Xiao Chaihu Tang requires careful consideration. This is why it is stated that clinicians must exercise prudent judgment. If the tongue coating is yellow, greasy, and dirty, or dry, rough, deep yellow, and thick/greasy, this is a sign that the exterior pathogen has entered the interior. Therefore, Da Chaihu Tang is appropriate for purgation.

Taiyuan Gan Cao (Licorice Root, honey-fried, 1 liang) Guifu Huashi (Talcum, 6 liang)
Grind each herb separately into fine powder. Take 5 qian per dose, add a small amount of fresh ginger juice and honey, and mix arbitrarily with decoction of Cong Bai (Allii Fistulosi Bulbus). For releasing the exterior, mix with decoction made from Dou Chi (Prepared Soybean) and Cong Tou (Scallion Head).

[Commentary by Jie] Ke Yunbo stated: "Huashi (Talcum) can clear the source of water above and unblock the water passages below, excreting via urination. Honey-fried Gan Cao (Licorice Root) possesses the harmonious nature of herbs, harmonizing the interior and exterior, stopping thirst, and generating fluids. Used as an assistant herb, it protects the primordial Qi (Yuan Qi) and drains deficient fire, thereby harmonizing the five Zang organs." Furthermore, regarding the original text's statement "For releasing the exterior, use Dou Chi and Cong Tou decoction," Cong Bai and Dou Chi constitute the ancient formula Cong Chi Tang (Scallion and Fermented Soybean Decoction), which is a crucial agent for treating new pathogens initially inducing latent heat. Thus, Zhang Luyu said, "Although the ingredients of this formula are light, its efficacy is remarkable. Whether for deficiency-type wind-heat with latent qi causing fever, or postpartum colds, it yields immediate results."