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In Taiyang disease, characterized by headache, fever, body ache, lower back pain, joint pain, aversion to cold, anhidrosis (absence of sweating), and wheezing, Mahuang Tang (Ephedra Decoction) is the primary prescription.

Cold is a Yin pathogen, and Ying (Nutritive Qi/Blood) is Yin in nature. When Yin pathogens invade the human body, they affect the Yin aspects. Thus, Cold injures Ying and Blood. Blood inherits the nature of Liver Qi, which is characterized by free flow and discharge (Shuxie). When Cold obstructs Ying-Yin, it loses its function of free flow and discharge, resulting in anhidrosis. The more Cold obstructs, the more severe the stagnation of Blood becomes, subsequently binding Wei (Defensive Qi) externally and causing it to store, manifesting as Cold. This indicates that Ying-Blood is injured while Wei-Qi is diseased. Therefore, although the pathology lies in Ying-Blood, the treatment focuses on Wei-Qi. In Mahuang Tang, Gancao (Licorice Root) protects the Middle Qi; Guizhi (Cinnamon Twig) disperses the stagnation in Ying; Mahuang (Ephedra Herb) vents the stagnation of Wei-Qi; and Xingren (Apricot Seed) benefits Lung Qi, descends rebellious Qi, and stops wheezing. Once the orifices open and the stagnation of Wei-Qi reaches outward, the Cold damage is cured.

Wei-Qi belongs to Yang and circulates externally in the skin and hair; Ying-Blood belongs to Yin and circulates internally in the meridians. The Lung stores Qi and governs Wei-Qi; the Liver stores Blood and manages Ying-Qi. Metal of the Lung has the nature of convergence, while Wood of the Liver has the nature of free flow and discharge; these are the natural properties of Yin and Yang. The Liver's nature is free flow and discharge, but the internal retention of Ying-Blood is controlled by the converging action of Lung Qi. The Lung's nature is convergence, but the external emission of Wei-Yang is facilitated by the discharging action of Liver Qi. Convergence results in anhidrosis, while free flow and discharge result in sweating. Wind injures Wei-Qi, causing disease in Wei rather than Ying. However, when Wei is constrained by Wind, it internally closes off Ying-Yin, leading to obstruction of Ying-Qi circulation, thus causing fever. Therefore, Guizhi (Cinnamon Twig) is used to vent heat in the channels and reach the stagnation in Ying. When Qi is diseased, blood-invigorating herbs are used because Qi injury affects Blood. Cold injures Ying-Blood, causing disease in Ying rather than Wei. However, when Ying is bound by Cold, it externally closes off Wei-Yang, preventing the diffusion of Wei-Yang, thus causing aversion to cold. Therefore, Mahuang (Ephedra Herb) is used to vent exterior Cold and reach the stagnation in Wei. When Blood is diseased, Qi-regulating herbs are used because Blood injury affects Qi. Guizhi vents the stagnation of Liver Blood, and Mahuang vents the stagnation of Lung Qi. Ying and Wei are respectively governed by the Lung and Liver but are collectively managed by the Taiyang channel. Hence, in the initial treatment of Wind-Cold affecting the Taiyang channel, Guizhi Tang (Cinnamon Twig Decoction) and Mahuang Tang (Ephedra Decoction) are established as the fixed methods.

Mahuang (Ephedrae Herba, 3 liang, remove joints)
Guizhi (Cinnamomi Ramulus, 1 liang, remove bark)
Gancao (Glycyrrhizae Radix et Rhizoma, 1 liang, honey-fried)
Xingren (Armeniacae Semen Amarum, 70 seeds, soak in boiling water, remove skin and tips, discard double-kernel seeds)

Take the above four ingredients, add 9 sheng of water, first boil Mahuang until the volume reduces by 2 sheng, skim off the foam on the surface, then add the remaining herbs. Boil until 2.5 sheng remains, strain, and take 8 he of the decoction warm. After ingestion, cover with blankets to induce a slight sweat. There is no need to drink hot porridge as in the method for Guizhi Tang; other post-medication care should follow the instructions for Guizhi Tang.