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Indicated for wind-cold pathogenic factors in the exterior, presenting with stiffness and pain in the head and nape, rigidity of the back, pulling and tightness (KT KT), floating pulse, absence of sweating, aversion to wind, accompanied by diarrhea; and also indicated for:
Ge Gen Tang (Kudzu Root Decoction)
Puerariae Lobatae Radix (Gegen, 葛根) (4 liang), Ephedrae Herba (Mahuang, 麻黄) (3 liang), Cinnamomi Ramulus (Guizhi, 桂枝), Paeoniae Radix Alba (Shaoyao, 芍药), Glycyrrhizae Radix et Rhizoma (Gancao, 甘草) (each 2 liang), Zingiberis Rhizoma Recens (Shengjiang, 生姜) (3 liang), Jujubae Fructus (Dazao, 大枣) (12 pieces). Use one dou of water. First decoct Mahuang and Gegen, reducing the volume by two sheng, skim off the foam, then add the remaining herbs. Decoct to obtain three sheng of liquid. Strain the dregs. Take one sheng warm. Cover with blankets to induce a slight sweat. There is no need to drink hot porridge to assist sweating.

Indicated for Taiyang-Yangming combined disease, which necessarily presents with spontaneous diarrhea and vomiting.
Add Banxia (Pinelliae Rhizoma, 半夏) half sheng (decocted first) to Ge Gen Tang.
The Mahuang in Ge Gen Tang, these two ingredients added to Gui Zhi Tang (Cinnamon Twig Decoction). (This is essentially Gui Zhi Tang with added Mahuang and doubled Gegen to dispel excess in the Ying level, a slight modification of the Mahuang and Guizhi methods.) Light substances can remove excess when there is no sweating. (Xu Zhicai stated: "Light substances can remove excess, referring to herbs such as Mahuang and Gegen.") When there is sweating, add Gegen but omit Mahuang. (This refers to the clause on Gui Zhi Jia Ge Gen Tang [Cinnamon Twig Decoction plus Kudzu Root], where the syndrome treated is similar. However, that formula omits Mahuang because sweating is already present; this formula adds Mahuang because sweating is absent.) Stiffness and tightness in the neck and back indicate Taiyang disease; use this formula when the pathogen just reaches the Yangming channel. (This is a formula for treating Taiyang pathogens just entering Yangming.) This formula can also treat Gang Jing (Stiff-Spasm). (Absence of sweating is called Gang Jing; presence of sweating is called Rou Jing [Soft-Spasm].) Symptoms include locked jaw, head tremor, and opisthotonos (backward arching of the back). (These are the manifestations of Jing disease.) For exterior wind-cold with diarrhea, (releasing the exterior will stop the diarrhea spontaneously; this is exterior-excess diarrhea, not interior-excess). If vomiting is present, adding Banxia is beneficial. (Named Ge Gen Jia Ban Xia Tang [Kudzu Root Decoction plus Pinellia]. For Taiyang-Yangming combined disease with diarrhea, Ge Gen Tang is used to resolve pathogens in both channels simultaneously. If vomiting occurs, add Banxia to stop vomiting. Formulas are established according to syndromes, each following specific principles.)
Ben Cao [Compendium of Materia Medica] states that Gegen clears severe heat. (Severe heat is a symptom of Yangming, hence its use.) It raises fluids and relieves thirst effectively. (Gegen is sweet and cool, generates fluids, has a light texture and ascending nature, and can guide clear Qi from the stomach upward. Therefore, it is commonly used for thirst and diarrhea.) Why would Zheng Yangming Bing (Standard Yangming Disease) use this? (Gegen is an exterior-releasing herb for Yangming channel disease. If it is Yangming Fu-organ disease, purgation is indicated, not sweating. Therefore, Zhang Zhongjing did not include formulas with Gegen in the "Standard Yangming Disease" chapter.) Li Dongyuan and others had not yet fully elaborated. (Li Dongyuan and others assigned drugs to channels, designating Gegen as the chief herb for Yangming, without distinguishing between Channel and Fu-organ diseases, indicating their theory was not yet exhaustive.)