伤寒以病因而为病名者也。温病热病。以天时与病形而为病名者也。由三者皆起于感寒
。或
者通以伤寒称之。夫伤寒即发于天令寒冷之时。而寒邪在表。闭其腠理。有恶风恶寒之症者
。因风寒在表表气受伤也。温病热病。后发于天令暄。热之时怫热自内达外。郁其腠理。无
寒在表。故无恶风恶寒之症。其有恶风恶寒之症者。重有风寒新中。而表气亦受伤故也。伤
寒汗下不愈而经者亦温病也温病之脉行在诸经随其经之所在而取之。
大头瘟者。足阳明邪热太甚。恣实少阳相火而为之炽。多在少阳。或在阳明。或传太阳
。视
其肿势在何部分。随经取之。湿热为肿。火盛则痛。此邪见于头。多在两耳前后。以先出为
主病也。治之不宜药速。速则过其病。所谓上热未除。中寒复生。况头乃空虚之部分。邪着
空虚。无所不至。治法当先缓而后急先缓者。用药性味俱缓。更缓服。以浸渍无形之邪也。
后急者。谓缓剂已泻。邪入于中。是到阴部染于有形质之所。若不速去。则损阴也。此却为
客
邪当急去之也。假令少阳阳明为病少阳为邪出于耳前后也。阳明为邪者。首大肿也。先以黄
芩黄连甘草。通炒过。煎汤少少不住服。或剂毕。再用大黄煨。鼠粘子炒香。煎成去滓。纳
芒硝。俱各等分。亦时时呷之。得微利。及邪气已。只服前药。如不已。再根据前次第服之。
取大便利。邪气即止。如阳明渴者。加石膏。少阳渴者。加栝蒌根。阳明行经。升麻芍药葛
根太阳行经羌活防风之类。
伤寒是以致病原因来命名疾病的。温病和热病，则是根据时令气候与病症表现来命名的。这三种病都起因于感受寒邪。因此人们有时统称为伤寒。所谓伤寒，是指发生在天气寒冷之时，寒邪侵袭体表，闭塞腠理，出现怕风、怕冷等症状，这是因为风寒在表，导致卫气受伤的缘故。
温病和热病，后来发生在天气温暖炎热之时，热气由内向外发散，郁闭腠理，体表没有寒邪，所以没有怕风、怕冷的症状。如果出现了怕风、怕冷的症状，是因为又新受了风寒，导致卫气再次受伤。
伤寒经过发汗或攻下治疗后未愈，转入经络的，也属于温病范畴。温病的脉象流行于各条经脉，应根据病变所在的经脉进行针刺治疗。
大头瘟，是由于足阳明经邪热过盛，助长少阳相火而使其炽烈所致。病位多在少阳经，或在阳明经，或传变至太阳经。需观察肿胀部位在哪个区域，随所属经脉选取穴位治疗。湿热导致肿胀，火邪旺盛则引起疼痛。这种邪气表现在头部，多集中在两耳前后，以先出现的症状为主病特征。
治疗时不宜用药过猛过快。药力过猛会损伤正气，导致“上部的热邪未除，中焦的寒邪又生”。况且头部是空虚的部位，邪气附着于空虚之处，无处不到。治疗方法应当先缓后急。“先缓”是指使用药性平和、气味清淡的药物，并且缓慢服用，以慢慢浸渍消散无形的邪气。“后急”是指当缓和的药剂已经泻去部分邪气，但邪气深入体内，进入阴分，沾染有形的实质组织时，若不迅速祛除，就会损伤阴液。此时对于客居的邪气应当急速祛除。
假如少阳经和阳明经发病：少阳经受邪表现为耳前耳后肿痛；阳明经受邪表现为头部肿大。先用黄芩、黄连、甘草，共同炒过后，煎汤少量多次持续服用。或者服完一剂后，再用煨大黄、炒香的鼠粘子（牛蒡子），煎成去渣，加入芒硝，各药分量相等，也是时时小口频服。使患者产生轻微腹泻，待邪气消除后，只服用前面的药物。如果病仍未愈，再按照之前的顺序服药，直到大便通畅，邪气即止。如果阳明经病患者口渴，加石膏；少阳经病患者口渴，加栝蒌根（天花粉）。若病在阳明经行经部位，加升麻、芍药、葛根；若病在太阳经行经部位，加羌活、防风之类。
Shanghan (Cold Damage) is named after its etiology. Wenbing (Warm Diseases) and Rebing (Heat Diseases) are named according to the seasonal climate and clinical manifestations. All three originate from contracting cold pathogens. Therefore, they are sometimes collectively referred to as Shanghan.
Shanghan occurs during cold weather, where cold pathogens invade the exterior, closing the Couli (pores and interstices), leading to symptoms of aversion to wind and cold. This is due to wind-cold residing in the exterior, injuring the Wei Qi (Defensive Qi).
Wenbing and Rebing occur later during warm or hot weather. Heat rises from within to the exterior, stagnating the Couli. There is no cold pathogen in the exterior; thus, there are no symptoms of aversion to wind or cold. If such symptoms appear, it indicates a new contraction of wind-cold, causing further injury to the Wei Qi.
If Shanghan fails to resolve after sweating or purging therapies and the pathogen enters the meridians, it transforms into a Wenbing pattern. The pulse of Wenbing circulates through the various meridians; treatment should target the specific meridian affected.
Datouwen (Great Head Plague) results from excessive heat pathogens in the Foot-Yangming Meridian, which intensifies the Ministerial Fire of the Shaoyang Meridian. The pathology primarily involves the Shaoyang or Yangming meridians, or may transmit to the Taiyang meridian. Treatment depends on observing the location of the swelling and selecting acupoints along the corresponding meridian. Damp-heat causes swelling, while excessive fire causes pain. This pathogen manifests on the head, mostly around the ears, with the initial symptoms indicating the primary disease site.
Treatment should not be overly aggressive or rapid. Rapid intervention may fail to clear the upper heat while generating middle-jiao cold. Moreover, the head is a hollow area; pathogens adhering to this void can spread everywhere. The therapeutic principle is "first slow, then urgent." "First slow" means using herbs with mild properties and flavors, administered slowly to gradually dissipate formless pathogens. "Then urgent" applies when the mild formula has cleared some pathogens, but the remaining pathogen has penetrated inward to the Yin levels and attached to substantial tissues. If not removed quickly, it will damage Yin fluids. At this stage, the exogenous pathogen must be expelled urgently.
For example, if both Shaoyang and Yangming meridians are involved: Shaoyang involvement presents as swelling around the ears; Yangming involvement presents as massive head swelling. Initially, use Huangqin (Scutellariae Radix), Huanglian (Coptidis Rhizoma), and Gancao (Glycyrrhizae Radix et Rhizoma), stir-fried together, decocted, and taken in small amounts frequently. After one dose, switch to Wei Dahuang (Prepared Rheum Palmatum Radix et Rhizoma), Chao Shuniuzi (Fried Arctii Fructus), decocted, strained, and mixed with Mangxiao (Natrii Sulfas), all in equal parts. Take frequently in small sips until slight diarrhea occurs. Once the pathogen is eliminated, resume the first formula. If unresolved, continue the sequence until bowel movements become free and the pathogen ceases. If the patient exhibits thirst due to Yangming involvement, add Shigao (Gypsum Fibrosum); if due to Shaoyang involvement, add Gualougen (Trichosanthis Radix). For pathogenic factors traveling along the Yangming meridian, add Shengma (Cimicifugae Rhizoma), Baishao (Paeoniae Radix Alba), and Gegen (Puerariae Lobatae Radix); for the Taiyang meridian, add Qianghuo (Notopterygii Rhizoma et Radix) and Fangfeng (Saposhnikoviae Radix).