Liu Hejian elucidated the theories in *Suwen: Yuanji* (Basic Principles of the Yellow Emperor's Inner Canon). There are thirty-three types of heat diseases in total; this is a general statement regarding the pathogenesis of diseases caused by heat pathogens. However, the "heat disease" mentioned in the *Shanghan Li* (Treatise on Cold Damage Examples) does not belong to this category. The principle here is similar to how the "wind strike" in the *Shanghan Li* is not viewed in the same manner as the "wind strike and joint pain diseases" in the *Jingui Yaolue*. Generally speaking, after transmission and transformation, wind-cold diseases mostly turn into heat syndromes. The most difficult time to distinguish them is at the initial stage of Taiyang disease (diseases affecting the Taiyang channel). Therefore, the "heat disease" in the *Shanghan Li* must be distinguished starting from the initial appearance of Taiyang disease symptoms such as headache, stiffness of the neck and nape, aversion to cold, and fever.

According to Zhang Zhongjing: "Taiyang heat strike is called Ye disease." Its manifestations include sweating, aversion to cold, body heat, and thirst. Zhang Zhongjing clearly identifies this as Ye disease, which aligns with what is stated in the *Neijing: Rebing Lun* (Treatise on Heat Diseases): "Diseases occurring before the Summer Solstice are called Warm diseases; those occurring after the Summer Solstice are called Summerheat diseases." For the same Taiyang disease, Warm diseases present with thirst but no aversion to cold; heat diseases (here referring to summerheat/Ye) present with both thirst and aversion to cold; wind strike presents with sweating but no thirst; cold damage presents with no thirst, aversion to cold, and absence of sweating; whereas heat disease presents with sweating, aversion to cold, and thirst. Zhang Zhongjing's differentiation of syndromes is so clear that it can be inferred his main treatment methods differ from those for wind, cold, dampness, etc. Because heat pathogens cause symptoms resembling cold damage, aversion to cold occurs conversely; because heat consumes body fluids, thirst appears. As for sweating and body heat, these are all signs of Yang pathogens being constrained and depressed. The *Jingui Yaolue* explicitly establishes the prescription of Renshen Baihu Tang (Ginseng White Tiger Decoction), utilizing its functions to benefit Qi, generate fluids, and eliminate irritability and heat. This provides a standard for people to follow. The later use of Liuyi San (Six-to-One Powder) inherits this intent. If one were to recklessly apply muscle-relaxing and diaphoretic methods to such diseases, few would avoid causing harm or delay. How can one fail to distinguish between different conditions presenting with the same Taiyang symptoms of head and neck stiffness, pain, and aversion to cold?

Question: Why does a patient with a heat disease experience aversion to cold? Answer: This meaning is clearly stated in the *Neijing*. The classic says: "Aversion to cold and shivering all belong to heat." It also states: "Trembling as if losing spiritual control all belong to fire." Thus, Liu Hejian said: When heat is severe, the patient may feel cold; this is due to heat disease, not actual cold. Fire constrained internally forces Yin outward; excessive Yang repels Yin, often manifesting as exterior cold syndromes. Moreover, aversion to cold accompanied by thirst is naturally different from the aversion to cold seen in wind strike or cold damage. One should directly clear the heat, and the exterior syndrome of aversion to cold will naturally resolve.

Furthermore, the *Nanjing* states: In heat diseases, the pulse is floating at both Yin and Yang positions; superficially it is slippery, deeply it is scattered and choppy. This is the normal pattern of pathogenesis. However, considering modern people, during the peak of summer heat, sitting or lying in drafts, or indulging in raw and cold foods, internal heat is bound by external cold. The heat becomes more constrained and cannot vent, thus leading to heat disease. Therefore, when discussing Taiyang summerheat strike, Zhang Zhongjing specifically lists two pulse patterns—string-taut, fine, hollow, slow; and weak—to exhaustively cover variations in disease presentation. This represents Zhang Zhongjing's flexible and adaptive methods of his time, intended to inspire the intuitive understanding of later practitioners. When encountering such syndromes, one should not use bitter-cold herbs to directly suppress the heat. Later generations treating summerheat diseases have used Dasun San (Great Harmony Powder) and Xiangru Yin (Elsholtzia Drink), precisely based on this principle.

Moreover, the *Neijing* states: "When humans are injured by cold, they develop heat diseases." Precisely because heat diseases also present with Taiyang symptoms like head and neck stiffness, pain, and aversion to cold, they can be analogized to the principles of cold damage. The ancient sages taught the method of nourishing growth during the three months of summer: go to bed late and rise early, do not dislike the sun, allow Qi to vent, just as heat received from outside should be allowed to dissipate externally. Heat certainly desires to vent outward and not be obstructed internally. The purport is profound.