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(This condition is also known as *Shixing Shanghan* [Seasonal Epidemic Cold Damage], and is commonly referred to as *Hanyi* [Cold Epidemic].)

[Etiology] In spring, warmth should prevail but cold prevails instead; in summer, heat should prevail but coolness prevails instead. Contracting these abnormal climatic conditions leads to disease. The symptoms are similar among people of all ages, and the disease is contagious. The reason for its contagion lies in the cold pathogen being accompanied by *Lifeng* [Violent Wind, a strong wind evil] or *Hui Shi* [Filthy Dampness, turbid dampness]. Although the clinical presentation resembles *Shanghan* [Cold Damage], the etiology shares similarities yet has distinct differences.

[Symptoms] At onset, there is headache, body pain, aversion to cold with high fever, absence of sweating, and no thirst. There may be chest fullness and nausea, or rebellious qi causing vomiting, or limb flaccidity and abdominal pain. The tongue coating is white and thin; in severe cases, it may appear pale gray and thinly greasy. If the pathogen transmits inward, symptoms such as thirst, constipation, deafness, and mental confusion may occur. The tongue coating changes from white to yellow, and then from yellow to black.

[Pulse] The left pulse is slightly tight (*Jin*), and the right pulse is wiry and slow (*Xuan Huan*).

[Treatment] After the Spring Equinox, if the disease arises due to accompanying *Lifeng*, and headache and aversion to cold are particularly severe, use *Suqiang Dabiao Tang* (Perilla and Notopterygium Decoction to Release the Exterior), adding fresh scallion white (3 qian) and light fermented soybean (4 qian), employing acrid-warm methods to release the exterior. Before the Autumn Equinox, if the disease arises due to accompanying *Hui Shi*, and body pain and limb flaccidity are particularly severe, use *Huoxiang Zhengqi Tang* (Patchouli Qi-Regulating Decoction) added with scallion and fermented soybean, employing acrid-light aromatic methods to diffuse. In both cases, add *Zijin Pian* (Purple Gold Tablet) to resolve toxicity. If complicated syndromes arise, treatment can follow the transmission patterns of standard *Shanghan*.

[Commentary by Xiu] Regarding *Shixing Hanyi* [Seasonal Cold Epidemic], Master Yu distinguishes between two etiologies: accompanying *Lifeng* and accompanying *Hui Shi*. By seeking the root according to the season and prescribing formulas based on symptoms, he demonstrates profound insight. If a patient has a constitution of innate Yang deficiency, and external cold directly invades the Yin meridians, suddenly causing vomiting, diarrhea, abdominal pain, cold limbs, and tendon spasm, this constitutes *Shixing Zhonghan* [Seasonal Mid-Cold]. It should be treated according to the principles of Yin-pattern *Shanghan*. Based on my experience, *Hanyi* occurs frequently in the fourth, fifth, sixth, and seventh lunar months. If the weather is sunny less often and rainy more often, with dampness prevailing, syndromes of *Shanghan* combined with dampness are common. Using *Huoxiang Zhengqi Tang* added with scallion, fermented soybean, and *Zijin Pian*, simultaneously inducing sweating and promoting urination to avoid filth and resolve toxicity, is indeed an accurate formula for this condition. If cold accompanies *Lifeng*, with pathogenic factors dominating the exterior and no latent heat in the interior, *Huo Ren Baidu San* (Person-Rescuing Detoxification Powder) can be used, 3–4 qian per dose, taken with soaked scallion and fermented soybean decoction, which also yields excellent results. Even using *Sheng San Zi* (Holy Mixture) to treat *Hanyi* shows significant efficacy.

[Annotation by Lian] When spring should be warm but is cold, and summer should be hot but is cool, contracting this non-seasonal cold is called *Hanyi* [Cold Epidemic]. When autumn should be cool but is hot, and winter should be cold but is warm, contracting this non-seasonal warmth is called *Wenyi* [Warm Epidemic]. These are the regular epidemics of the four seasons, collectively termed *Shiyi* [Time Epidemic]. In recent times, *Hanyi* is rare, while *Wenyi* is common; physicians should pay particular attention. The former scholar Wu Kun'an stated: "When treating *Shiyi*, one must distinguish whether the heavenly climate is cold or warm, dry or damp, and assess the patient's deficiency/excess and labor/rest. Treatment must be tailored to the syndrome and cannot be rigidly applied." For instance, during prolonged droughts, the climate is dry, and *Wenyi* spreads; clearing fire and resolving toxicity is appropriate, while avoiding drying agents. During prolonged rains, the climate is damp, and people often suffer from *Hanyi*, possibly with vomiting and diarrhea; drying dampness and dispersing cold is appropriate, while avoiding moistening agents. This is the orthodox method for treating *Shiyi*.