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The *Huoren Shu* (Book of Vitality) states: After taking Mahuang Tang (Ephedra Decoction), if the patient experiences mental restlessness and dizziness, epistaxis (nosebleed) will inevitably occur; after taking Guizhi Tang (Cinnamon Twig Decoction), if vomiting occurs, hematemesis with pus and blood will inevitably follow later. For headache, fever, absence of sweating, and aversion to wind, Mahuang Tang is appropriate; this indicates a case requiring exterior resolution using Ephedra. For headache, fever, presence of sweating, and aversion to wind, Guizhi Tang is appropriate; this indicates a case requiring dispersion of pathogenic factors using Cinnamon Twig. Both formulas are used for resolving the exterior, but they differ in addressing mild versus severe conditions, which must be carefully distinguished. Zhang Zhongjing stated: Patients without sweating should not take Guizhi Tang, and patients with sweating should not take Mahuang Tang. Ancient practitioners held that patients with sweating should undergo muscle-releasing therapy, while those without sweating should undergo sweating-inducing therapy. This shows that even within the Taiyang disease (disease of the Taiyang channel), there are distinctions, let alone failing to differentiate between Yin and Yang patterns before prescribing. If sweating-inducing therapy is indicated but purgation is mistakenly used, death ensues; if purgation is indicated but sweating-inducing therapy is mistakenly used, death also ensues. Hence it is said: Once Guizhi Tang is swallowed, if Yang Qi is excessive, death results; (This refers to cases where purgation was indicated but sweating-inducing therapy was used instead. In cases of excess Yang, internal heat exists with pathogens located in the interior, so purgation is indicated. Administering Guizhi Tang to induce sweating in such cases leads to death due to excess Yang.) Once Chengqi Tang (Gut-Purging Decoction) enters the stomach, if Yin Qi is excessive, demise follows. (This refers to cases where sweating-inducing therapy was indicated but purgation was used instead. In cases of excess Yin, aversion to cold exists with pathogens located in the exterior, so sweating-inducing therapy is indicated. Mistakenly administering Chengqi Tang for purgation leads to demise due to excess Yin.) Thus, the use of Mahuang Tang, Guizhi Tang, and Chengqi Tang determines life or death; medical practitioners must certainly exercise caution!

In Shanghan disease (Cold Damage), after three or four days, if various decoctions fail to cure the illness, and the patient presents with fever and a rapid pulse, indicating that the pathogen remains in the meridians and has not entered the Zang-Fu organs, Guizhi Shigao Tang (Cinnamon Twig and Gypsum Decoction) is the primary treatment. This formula can replace Guizhi Tang after the Summer Solstice; if Ephedra is added, it can replace Mahuang Tang or Qinglong Tang (Azure Dragon Decoction). Presence of sweating and a slow pulse indicate a Guizhi Tang pattern; absence of sweating and a tight pulse indicate a Mahuang Tang or Qinglong Tang pattern.

The *Zhengzhi Lun* (Treatise on Diagnosis and Treatment) states: Baihu Tang (White Tiger Decoction) has a cooling nature and is only used after the Summer Solstice. For instance, in regions where the ground remains hot in the seventh and eighth lunar months, if a patient suffers from high fever, observing the condition allows for the continued use of Baihu Tang, after which sweating naturally occurs and the disease resolves. However, since Baihu Tang contains Shigao (Gypsum Fibrosum), it also treats Shanghan disease and is not exclusively for treating Zhongshu (Heatstroke/Summerheat). One might ask: If, during summer, one indeed observes patterns suitable for Mahuang Tang or Guizhi Tang, how can one refrain from using them and insist on using Baihu Tang? The answer is: This perspective is particularly profound, but one must apply it flexibly according to the immediate clinical presentation. For example, weak individuals or the elderly should not take Baihu Tang, as its nature is cooling; patients with diarrhea and abdominal pain should avoid it and instead take Xiaochaihu Tang (Minor Bupleurum Decoction). Another question arises: Can Baihu Tang be used by everyone after the Summer Solstice? The reply is: Baihu Tang is merely one type of formula for resolving the exterior in cases of Zhongshu and post-sweating conditions; it is not a standard medicine for Zheng Shanghan (True Cold Damage). Current physicians often attribute illnesses in the sixth month to Zhongshu without distinguishing true heat diseases, leading to the use of overly cooling medications. Moreover, since Yin Qi resides internally during summer, extreme caution is warranted. The *Zhengzhi Lun* states: Baihu Tang also treats Shanghan disease, not just Zhongshu. The *Huoren Shu* states: Baihu Tang is merely one type of formula for treating Zhongshu and resolving the exterior after sweating. Although these two statements differ slightly, generally speaking, one must assess the condition according to the time and circumstances, use it when appropriate, and not adhere rigidly to a single viewpoint.