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Lei Shaoyi stated: The *Yizong Jinjian* (Golden Mirror of Medical Practice) records: The classics state, "If one is injured by cold in winter, one will inevitably suffer from warm disease in spring; by summer, it becomes heat disease." Heat disease refers to the slight coldness within the normal seasonal climate of winter, which does not cause immediate illness. Ni Shi believed that after the beginning of Summer (Lixia), the long-pent-up pathogenic qi is triggered by the heat of the season. Therefore, upon initial onset, there is fever, sweating, thirst, and irritability, without aversion to cold but rather aversion to heat, accompanied by a large pulse. This constitutes heat disease. The *Yitong* states: Since the pathogen is not directly external, there is only heat without aversion to cold; since the heat originates internally, there is dry mouth, thirst, and excessive drinking. Once the pathogen has stagnated and transformed into heat, it can no longer be described as cold. Synthesizing these views, the etiology of heat disease caused by latent qi (pent-up pathogenic factors) becomes clear. However, compared to "late-onset" diseases (winter cold manifesting in spring), it manifests even later; compared to general warm diseases, it lies deeper in latency. At the initial stage, the method of clearing heat and venting pathogens should be used. If the heat intensity does not subside, the method of clearing heat and purging fire should follow. If aversion to cold coexists with a superficially floating and tight pulse, this indicates sudden cold attack in summer, where cold is on the exterior and heat is on the interior. One should first use acrid-warm exterior-releasing methods to vent the exterior; once the exterior pathogen is resolved, cool agents should be used to purge the interior heat. If there is no floating-tight pulse or aversion to cold, and acrid-warm formulas are mistakenly used, depleting body fluids, the method of clearing heat and preserving fluids should be employed, adding American Ginseng (*Panax quinquefolius*) and Gypsum (*Shigao*). If accompanied by aversion to wind and slight sweating, with a superficially floating and slow pulse, this indicates wind pathogen on the exterior with heat on the interior; acrid-cool exterior-releasing methods should be used to resolve the exterior first. Regarding dry tongue coating, delirium, and manic stupor, urgently apply the method of clearing heat and purging fire, adding Zixue Dan (Purple Snow Pill). For macules, add Coptis Rhizome (*Huanglian*) and Gardenia Fruit (*Zhizi*); for papules/rash, add Lotus Leaf (*Heye*) and Arctium Fruit (*Niubang*). It must be understood that heat disease easily damages Yin; thus, preserving Yin at all times is paramount. Acrid-warm agents that consume fluids should not be used recklessly.

Yang Ruhou stated: After the Summer Solstice, intense heat commands the season, and Minister Fire (*Xianghuo*) is active. If a person presents with fever, body pain, no aversion to cold, but severe heat and severe thirst, this is called heat disease. The *Neijing·Re Lun* states: "All cases where Shanghan transforms into warm disease manifest as warm disease before the Summer Solstice and as summerheat disease after the Summer Solstice." Summerheat disease is heat disease. Before the Summer Solstice, when the climate is not yet hot, it is the warmth of spring, so the disease is still named warm disease. Warmth is the gradual progression toward heat. After the Summer Solstice, as the climate gradually heats up, becoming the summerheat of summer, the disease is named heat. The *Shanghan Xuli* states: "Summerheat disease involves heat more severe than warm disease." Thus, summerheat disease is essentially heat disease. Latent qi stagnates for a long time before manifesting; upon manifestation, there is severe heat and thirst. Zhang Zhongjing established Baihu Tang (White Tiger Decoction), which is actually the principal formula for treating heat disease. Heat disease develops from below upward and from inside outward, necessarily passing through the Yangming channel. Therefore, regardless of which Yang channel is involved, Gypsum (*Shigao*) with its acrid-cool nature is used to ascend and disperse the pathogen along with the trend; Anemarrhena Rhizome (*Zhimu*) with its bitter-cold nature calms the source of latent pathogens in the Shaoyin channel; Licorice Root (*Gancao*) and Rice (*Jingmi*) maintain the Qi of the Middle Jiao. This is a comprehensive and effective approach.

Yang Shangshan stated: Winter injury by cold, if mild, manifests as warm disease before the Summer Solstice; if severe, it manifests as summerheat disease after the Summer Solstice.

Shen Zonggan stated: This describes the general rule. However, there are also heat diseases in spring and warm diseases in summer. Warmth is lighter heat; heat is heavier warmth. Therefore, ancients often used the terms interchangeably.