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(Original Disease Collection)

Shanghan (Cold Damage), is a disease named according to its etiology. Wenbing (Warm Diseases) and Rebing (Heat Diseases) are named according to the seasonal climate and clinical manifestations. Since all three originate from external pathogenic invasion, they are collectively referred to as "Shanghan." The reason for this collective term lies in tracing the source of the cause. However, regarding medication, one cannot apply a uniform treatment method. Why? When humans contract cold pathogens after the Frost's Descent solar term but before the Spring Equinox, it typically occurs during the period of severe cold weather, with symptoms appearing immediately upon infection. Cold pathogens close the Couli (pores and interstitial spaces of the skin and muscles); therefore, only pungent, sweet, and warm agents are sufficient to disperse them. This is why Zhang Zhongjing must utilize formulas such as Guizhi Tang (Cinnamon Twig Decoction) and Mahuang Tang (Ephedra Decoction). In contrast, Wenbing and Rebing may involve cold pathogen exposure between Frost's Descent and Spring Equinox, but do not manifest immediately. The cold pathogen lies dormant within the muscles until the warm and hot weather of spring and summer causes internal heat to surge outward, obstructing the Couli. At this stage, there is no cold pathogen on the exterior. Such conditions require pungent and cool agents to resolve them; hence, Guizhi Tang and Mahuang Tang are not used. Formulas such as Chonghe Tang (Harmonizing Decoction), Tongjie San (Unblocking Exterior Powder), and Jiexi Tang (Releasing Muscle Decoction), which harmonize the interior and exterior, are applicable here.

In immediate-onset Shanghan, symptoms of aversion to wind or cold occur because wind-cold pathogens reside on the exterior, injuring the Wei Qi (Defensive Qi) of the surface. In delayed-onset Wenbing and Rebing, if symptoms of aversion to wind or cold appear, it is due to a new contraction of wind-cold, further injuring the Wei Qi. Without new wind-cold invasion, these symptoms would not exist. Even if they occasionally occur, it is because the patient's superficial Qi was originally deficient; as heat reaches the exterior, it further damages the Wei Qi, making the patient susceptible to wind and cold. This is not simply that wind injury causes aversion to wind and cold injury causes aversion to cold; rather, deficiency of Wei Qi leads to aversion to wind, and deficiency of Ying Qi (Nutritive Qi) leads to aversion to cold. Thus, Zhang Zhongjing stated: In Taiyang Bing (Disease of the Taiyang Channel), fever accompanied by thirst and absence of aversion to cold indicates Wenbing. Absence of aversion to cold implies the pathogen is not exogenous; thirst indicates intense internal heat. Wenbing presents thus, and Rebing can be inferred similarly. Any case presenting without thirst and with aversion to cold is clearly not Wenbing or Rebing.

However, Wenbing and Rebing may initially present with exterior syndromes before progressing inward. Due to internal stagnation and heat surging outward, heat becomes trapped in the Couli and cannot vent externally, causing it to revert inward and form excess syndromes amenable to purgation. This differs from Shanghan, which begins at the exterior. Those who fail to comprehend this logic might seek a floating-tight pulse (Fu Jin Mai) in spring-summer heat diseases, which is highly negligent. One must know that a tight pulse indicates cold pathogens; it appears only when cold pathogens are present. Is this the natural state of heat diseases? Others, unfamiliar with pulse morphology, mistake a wiry pulse (Xian Mai) for a tight pulse, diagnose cold, and treat erroneously. A vigorous and forceful pulse often manifests as wiry; it should not be mistaken for tight or diagnosed as cold. The pulse in heat diseases usually resides deeper in the muscle layer rather than being very superficial, and the right hand pulse is often stronger than the left, indeed due to internal stagnation. If the left hand pulse is strong or superficial, it indicates a severe re-infection with wind-cold; otherwise, it is not a heat disease but an acute wind-cold contraction. Generally, heat diseases lack signs of re-infection on the exterior; even if present, interior heat predominates, so cases without thirst are rare. Treatment should primarily focus on clearing heat, supplemented by releasing the exterior. Sometimes, treating the interior resolves the exterior spontaneously. I have often observed that when people treat heat diseases, erroneous purgation of the interior may not cause major harm, whereas erroneous diaphoresis (sweating) to release the exterior can lead to unpredictable complications. This sufficiently proves that heat originates internally and moves outward. Cases where erroneous purgation caused severe harm were actually epidemic conditions caused by sudden cold in spring and summer, where pathogens remained purely on the exterior without entering the interior. How can these be discussed together with heat diseases?

Because the world conflates heat diseases with Shanghan, people often confuse cold and heat concepts, seeking floating-tight pulses and using warm-hot medications. Furthermore, medical texts often conflate "Four Seasons Shanghan," treating spring-summer heat diseases identically to autumn-winter Shanghan without distinction. It is unknown that autumn-winter Shanghan represents true Shanghan, while spring-summer Shanghan represents epidemics. These are distinct paths from Wenbing and should not be treated alike. Moreover, Shanghan involves direct injury to the Yin channels and Taiyang channel. Although less likely to transform into stagnant heat, transmission to Yin channels results in cold syndromes requiring warming methods, which is vastly different from heat diseases; how can they be treated recklessly? Some understand part but not all, claiming Zhang Zhongjing’s exterior-releasing drugs are unusable today, while interior-purgative drugs are usable. Alas! Where exactly lie the principles of usability and non-usability? For conditions caused by miasma of seasonal irregular qi, or those transformed by re-infection with heterogeneous qi, one must observe the timing and nature of the qi, reference methods from both Shanghan and Wenbing, and adjust treatments accordingly. It is especially inadvisable to universally apply Zhang Zhongjing’s formulas for immediate-onset Shanghan.