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Ephedrae Herba (Mahuang, 麻黄) [removed nodes, 3 liang], Cinnamomi Ramulus (Guizhi, 桂枝) [washed, 2 liang], Armeniacae Semen Amarum (Xingren, 杏仁) [removed skin and tips, 70 seeds], Glycyrrhizae Radix et Rhizoma (Gancao, 甘草) [1 liang, raw].

Taiyang Shanghan (Cold Damage affecting the Taiyang channel), characterized by headache, fever, body ache, lower back pain, stiffness and difficulty in moving the joints, aversion to cold, absence of sweating, and wheezing, with a tight pulse at both the Cun (inch) and Chi (cubit) positions, is primarily treated with Mahuang Tang.

The Foot-Taiyang Bladder Channel originates from the inner canthus of the eye and follows the head, back, and waist; therefore, pain and stiffness occur in the areas it traverses. When pathogenic Cold binds the exterior, the body's Yang Qi cannot be dispersed and vented, leading to fever. With Cold pathogen at the exterior, the body loses its ability to withstand cold, resulting in aversion to cold. Cold has the nature of closure and storage, causing anhidrosis (absence of sweating). Since the body's Yang Qi cannot be dispersed outward, it must become congested internally, leading to wheezing. The nature of Cold Qi is rigid and forceful, causing a tight pulse. The morphology of Mahuang is hollow and empty; its flavor is pungent, warm, and light. Being hollow allows it to open the Couli (pores and interstices); being pungent allows it to disperse Cold pathogen; thus, it serves as the Jun (Emperor/Chief) herb. Guizhi is used as a Zuo (Assistant) herb for its ability to resolve the muscle layer; Xingren is used as a Zuo herb for its ability to promote the free flow of Qi; Gancao is added, adhering to the principle that Pungent and Sweet flavors together facilitate dispersion. Indeed, for Taiyang disease with anhidrosis, the use of Mahuang is established! However, if one does not carefully consider the patient's deficiency or excess constitution, nor the seasonal variations in cold and warmth, there is a warning against excessive sweating leading to Wang Yang (collapse of Yang). For excessive sweating, dusting powder is appropriate; for collapse of Yang, Fuzi Tang is appropriate.

Puerariae Lobatae Radix (Gegen, 葛根) [4 liang], Ephedrae Herba (Mahuang, 麻黄) [removed nodes, 3 liang], Cinnamomi Ramulus (Guizhi, 桂枝) [washed, 2 liang], Paeoniae Radix Alba (Shaoyao, 芍药) [2 liang, stir-fried], Glycyrrhizae Radix et Rhizoma (Gancao, 甘草) [2 liang].

In Taiyang disease, if there is stiffness and rigidity of the neck and back, anhidrosis, and aversion to wind, it is named Gang Jing (Stiff Spasm characterized by lack of sweat), which is primarily treated by this formula.

When Wind-Cold damages the "Jing" (channels/meridians) of the collaterals, the affected area experiences only pain, not yet reaching stiffness. When Wind-Cold damages the "Jin" (sinews/tendons) of the bones and sinews, the affected area exhibits tense, stiff, and straightened sinews, forming spasms. "Jing" (spasm) was a textual error in the original manuscript. Referring to it as Gang Jing indicates the name for cases without sweat. Materia Medica states: "Light substances can remove excess." Gegen and Mahuang are herbs with light morphology and qi; here, because of Exterior Excess due to Wind-Cold, these two are added to Guizhi Tang. Furthermore, when Taiyang and Yangming channels are simultaneously affected (He Bing), spontaneous diarrhea inevitably occurs. Diarrhea is a Interior syndrome. Ordinary physicians of today claim this is "Lou Di Shanghan" (leaky-bottom Cold Damage) and declare it incurable, whereas Zhang Zhongjing treats it with this formula. This is because when pathogenic Qi merges into the Yang aspect, Yang becomes Excess while Yin becomes Deficient; Yin deficiency leads to diarrhea. Administering this decoction to scatter the Exterior pathogen within the channels resolves the Yang Excess and harmonizes Yin, causing the diarrhea to cease spontaneously without specific treatment for the interior. This is truly profound, understood only by the wise.