冬为伤寒，春为温病，夏为暑病，秋为疟。
一岁长幼病相似，为温疫。多眠、多汗、脉浮，为风温。一身尽痛，为湿。身反张，为 。
阴阳大论曰∶春气温和，夏气暑热，秋气清凉，冬气冷冽，此四时正气之序也。冬时严寒，万类深藏，若
能固密，则不伤于寒，触冒之者，乃名伤寒耳。其伤于四时之气，皆能为病，惟伤寒为毒者，以其最为杀厉之
气也。中而即病者为伤寒，不即病者为寒毒，藏于肌肤中，至春变为温病，至夏变为暑病。暑病者，热极重于
温也。是以辛苦之人，春夏多温热病，皆由冬时触寒所致，非时行之气也。
凡时行者，春时应暖而反大寒，夏时应热而反大凉，秋时应凉而反大热，冬时应寒而反大温，此非其时而
有其气，是以一岁之中，长幼之病多相似者，此则时行之气也。
从春分以后至秋分节前，天有暴寒者，皆为时行寒疫也。三月四月，或有暴寒，其时阳气尚弱，为寒所折，
病热犹轻。五月六月，阳气已盛，为寒所折，病热则重。七月八月，阳气已衰，为寒所折，病热亦微。其病与
温病及暑病相似，但治有殊者，要在辨其病原寒、热、温三者之异，则用药冷热之品味判然矣。
其冬有非节之暖者，名冬温。冬温之毒，与伤寒大异。冬温复有先后，更相重沓，亦有轻重，治亦不同。
（冬温应常纪者有三∶岁少阴司天之政，五之气；阳明司天之政，终之气；厥阴司天之政，终之气。皆病冬温。
其不应常纪而反常者，则不可候之，而随时变易也。）气候亦有应至而不至者，或有未应至而至者，或有
至而太过者，皆成病气也。
凡四时伤寒，通宜补散。故丹溪治伤寒，多用补中益气汤。气虚者，四君子汤加发散剂。血虚者，四物汤
加发散剂。东垣治风湿，用补中益气加羌活、防风、升麻、 本、苍术。海藏治风湿无汗者，用神术汤，有汗
者，用白术汤；治刚 ，用神术汤加羌活、麻黄，治柔 用白术汤加桂心、 、术；治风湿用白术汤随
证加药；治中 脉弦细芤迟者，用黄 汤。此皆与仲景所谓辛苦之人，触冒之病伤寒同意也。
〔丹〕仲景论伤寒而未及乎中寒，先哲治冒大寒昏中者，用附子理中汤，其议药则得之矣。曰伤、曰中，
未有议其异同者。夫伤寒有即病，有不即病，因其旧有郁热，风寒外束，肌腠自密，郁发为热，病邪循经而入，
以渐而深，初用麻黄、桂枝辈微表而安，以病体不甚虚也。若中寒则仓卒感受，其病即发而暴，因其腠理疏豁，
一身受邪，难分经络，无热可发，温补自解，此气大虚，不急治则死矣。
伤寒、伤暑、伤湿，亦如伤寒之渐入也。中风、中暑、中湿，亦如中寒之暴受也。中寒治法见卒中暴厥门。
Cold damage in winter is termed Shanghan (Winter Cold Damage), warm disease in spring is termed Wenbing (Warm Disease), summerheat disease in summer is termed Shubing (Summerheat Disease), and malaria in autumn is termed Nue (Malaria).
If people of all ages within a year suffer from similar illnesses, it is called Wenyi (Warm Epidemic). Symptoms of excessive sleepiness, profuse sweating, and a floating pulse indicate Fengwen (Wind-Warmth). Generalized body pain indicates Shi (Dampness). Opisthotonos (rigid extension of the body) indicates Jing (Spasm).
The *Yin Yang Da Lun* states: The Qi of spring is mild and harmonious, the Qi of summer is hot and sultry, the Qi of autumn is cool and clear, and the Qi of winter is cold and biting; this is the sequence of the righteous Qi of the four seasons. In winter, severe cold causes all things to hide deeply. If one can maintain solidity and closure, one will not be injured by cold; those who are exposed to and offend against the cold are said to have contracted Shanghan (Winter Cold Damage). Injury by the Qi of the four seasons can all lead to disease, but among them, Shanghan is the most toxic because it is the most lethal pathogenic factor. Those who contract it and fall ill immediately are diagnosed with Shanghan (Winter Cold Damage); those who do not fall ill immediately harbor Han Du (Cold Toxin) within the skin and muscles, which transforms into Wenbing (Warm Disease) in spring and Shubing (Summerheat Disease) in summer. Shubing (Summerheat Disease) involves heat that is more extreme than that of Wenbing (Warm Disease). Therefore, laborers often suffer from warm-heat diseases during spring and summer, all caused by offending cold in winter, rather than by the Qi of the current season (Shixing Zhi Qi).
Whenever there is a pandemic or epidemic trend, it refers to situations where spring should be warm but is instead severely cold, summer should be hot but is instead excessively cool, autumn should be cool but is instead severely hot, and winter should be cold but is instead overly warm. This is an abnormal climate occurring out of season. Consequently, throughout the year, illnesses among both young and old tend to be similar; this is known as Shixing Zhi Qi (Epidemic Qi of the Season).
From after the Spring Equinox until before the Autumn Equinox, sudden cold spells are all classified as Shixing Hanyi (Epidemic Cold). In March and April, sudden cold may occur; at this time, Yang Qi is still weak, suppressed by cold, resulting in milder heat symptoms. In May and June, Yang Qi is abundant; suppressed by cold, the resulting heat symptoms are severe. In July and August, Yang Qi is declining; suppressed by cold, the heat symptoms are also mild. These illnesses resemble Wenbing (Warm Disease) and Shubing (Summerheat Disease), but their treatments differ significantly. The key lies in distinguishing whether the pathogen is cold, heat, or warmth; thus, the choice between cooling and warming herbs becomes clear.
When winter exhibits unseasonal warmth, it is called Dongwen (Winter Warmth). The toxicity of Dongwen (Winter Warmth) differs greatly from Shanghan (Winter Cold Damage). Dongwen (Winter Warmth) has variations in onset timing and severity, leading to different treatment approaches. (There are three regular patterns for Dongwen (Winter Warmth): when Shaoyin (Lesser Yin) governs the Heaven’s policy during the fifth period; when Yangming (Greater Yang) governs during the final period; and when Jueyin (Terminal Yin) governs during the final period. All result in Dongwen (Winter Warmth). Abnormal cases that deviate from these regular patterns cannot be predicted and must be adjusted according to changing circumstances.) Climate may also fail to arrive when expected, arrive prematurely, or arrive with excessive intensity; all such anomalies become pathogenic factors.
Generally, for Shanghan (Winter Cold Damage) occurring in any season, the appropriate approach is tonification combined with dispersion. Thus, Zhu Danxi treated Shanghan (Winter Cold Damage) primarily using Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction). For patients with Qi deficiency, Sijunzi Tang (Four Gentlemen Decoction) was used with added dispersing agents. For patients with Blood deficiency, Siwu Tang (Four Substances Decoction) was used with added dispersing agents. Li Dongyuan treated Wind-Dampness using Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction) plus Qianghuo (Notopterygii Rhizoma et Radix), Fangfeng (Saposhnikoviae Radix), Shengma (Cimicifugae Rhizoma), Gaoben (Ligustici Rhizoma et Radix), and Cangzhu (Atractylodis Rhizoma). Zhang Yuansu (Haizang) treated Wind-Dampness without sweating using Shenzhu Tang (Divine Skill Decoction), and with sweating using Baizhu Tang (Atractylodes Macrocephala Decoction). For Gangjing (Stiff Spasm), he used Shenzhu Tang (Divine Skill Decoction) plus Qianghuo (Notopterygii Rhizoma et Radix) and Mahuang (Ephedrae Herba); for Roujing (Flaccid Spasm), he used Baizhu Tang (Atractylodes Macrocephala Decoction) plus Guixin (Cinnamomi Cortex) and Fuzi (Aconiti Lateralis Radix Praeparata). For Wind-Dampness, he used Baizhu Tang (Atractylodes Macrocephala Decoction) with modifications based on symptoms. For Zhonghan (Mid-Cold) presenting with a string-tight, fine, hollow, or slow pulse, he used Huangqi Jianzhong Tang (Astragalus Decoction to Establish the Middle). All these approaches align with Zhang Zhongjing’s view that laborers contracting cold leads to Shanghan (Winter Cold Damage).
[Zhu Danxi] Zhang Zhongjing discussed Shanghan (Winter Cold Damage) but did not address Zhonghan (Mid-Cold). Earlier sages treated patients who fainted due to exposure to severe cold using Fuzi Lizhong Tang (Aconite Decoction to Regulate the Middle), demonstrating sound reasoning in their herbal prescriptions. However, no one had previously discussed the differences between "Shang" (Injury) and "Zhong" (Strike/Mid). Shanghan (Winter Cold Damage) can manifest immediately or be delayed. Because the interior already contains stagnant heat, and wind-cold binds the exterior while the pores remain closed, the stagnation generates heat, and the pathogen enters via the meridians, gradually deepening. Initially, mild diaphoresis with herbs like Mahuang (Ephedrae Herba) and Guizhi (Cinnamomi Ramulus) is used to settle the condition, as the body constitution is not severely deficient. In contrast, Zhonghan (Mid-Cold) results from sudden exposure; the illness manifests abruptly and violently. Because the pores are open and the entire body is affected, it is difficult to localize the pathogen to specific meridians. There is no heat to release via sweating; instead, warming and tonifying therapies resolve the condition. This occurs because of severe Qi deficiency; if not treated urgently, death will ensue.
Shanghan (Winter Cold Damage), Shangshu (Summerheat Injury), and Shangshi (Dampness Injury) progress gradually, similar to Shanghan (Winter Cold Damage). Zhongfeng (Wind Strike), Zhongshu (Summerheat Strike), and Zhongshi (Dampness Strike) occur suddenly, similar to Zhonghan (Mid-Cold). The treatment methods for Zhonghan (Mid-Cold) are detailed in the section on Stroke and Sudden Syncope.