发热翕翕无停止时，外覆之表热也。发热蒸蒸如炊笼，内越之里热也。表热尿白，里热尿赤。表热无汗，
宜麻黄汤，有汗宜桂枝汤。里热轻者，宜凉膈散，重者宜三承气汤。发热兼口燥舌干烦渴者，为阳经之热
，真热也，宜白虎等汤。发热兼厥冷下利清谷者，为阴经之热，假热也，宜四逆等汤。
发热恶寒，发于阳表也。有汗宜桂枝汤，无汗宜麻黄汤。无热恶寒，发于阴里也。有汗宜桂枝加附子汤，
无汗宜麻黄附子细辛汤。背恶寒，口中不燥而和，属少阴，宜附子汤。背恶寒，口中燥而渴，属阳明，宜白虎
加人参汤。
风寒二者，大率多相因，而少相离。有寒时不皆无风，有风时不皆无寒，故三阳俱有恶寒恶风同见也。恶
风与恶寒，均属表病，法当从表。然风属阳，寒属阴，故三阴经证，有恶寒而无恶风也。
三阳经头痛，身皆发热，法当从三阳治。若不大便，小便
赤，为里热已实，宜承气汤下之。若小便清白，即不大便，为里热未实，表尚未清，法当先从表治也。厥阴
头痛，多厥而无热，呕吐涎沫，是厥阴挟寒邪上逆也，宜吴茱萸汤，温而降之。三阴经，无头痛，惟厥阴经
有头痛，以其脉与督脉上会于巅也。三阴经，无发热，厥阴，少阴亦有发热，谓之反发热，以其脏有相火，
阴盛格阳于外也。
发热感觉像羽毛覆盖般温和且持续不停，这是体表的热证。发热感觉像蒸笼中热气腾腾向外散发，这是体内的热证。表热证小便颜色清白，里热证小便颜色红赤。表热证无汗，适宜使用麻黄汤；若有汗出，适宜使用桂枝汤。里热证病情较轻的，适宜使用凉膈散；病情较重的，适宜使用三承气汤（大承气汤、小承气汤、调胃承气汤）。发热兼有口燥舌干、烦躁口渴症状的，属于阳经的热证，是真热证，适宜使用白虎汤等方剂。发热兼有四肢厥冷、下利清谷（泻下未消化的食物）症状的，属于阴经的热证，是假热证，适宜使用四逆汤等方剂。
发热并伴有恶寒（怕冷），病发于阳分体表。有汗出的适宜使用桂枝汤，无汗出的适宜使用麻黄汤。没有发热只感到恶寒，病发于阴分体内。有汗出的适宜使用桂枝加附子汤，无汗出的适宜使用麻黄附子细辛汤。背部怕冷，口中不干燥且神态平和，属于少阴病，适宜使用附子汤。背部怕冷，口中干燥且口渴，属于阳明病，适宜使用白虎加人参汤。
风邪和寒邪两者，大体上多相互伴随，很少分离。有寒邪时不一定没有风邪，有风邪时不一定没有寒邪，所以三阳经都可能出现恶寒和恶风同时存在的症状。恶风（遇风则怕）与恶寒，都属于表病，治疗法则应当从解表入手。然而风属阳，寒属阴，所以在三阴经的证候中，只有恶寒而没有恶风。
三阳经引起的头痛，身体都会发热，治疗法则应当从三阳经论治。如果大便不通，小便红赤，说明里热已经结实，适宜用承气汤攻下。如果小便颜色清白，即使大便不通，说明里热尚未结实，表邪也未清除，治疗法则应当先从解表入手。厥阴经引起的头痛，大多表现为四肢厥冷而无发热，伴有呕吐涎沫，这是厥阴经挟带寒邪上逆所致，适宜使用吴茱萸汤，以温降之法治疗。三阴经通常没有头痛，只有厥阴经有头痛，因为其经脉与督脉在头顶交会。三阴经通常没有发热，但厥阴经和少阴经也可能出现发热，称为“反发热”，这是因为脏腑内有相火，阴寒过盛将阳气格拒于体外所致。
Fever that feels gentle like feathers covering and persists without stopping is exterior heat (Biao Re). Fever that feels steaming hot like a cooking steamer, radiating outward from within, is interior heat (Li Re). In exterior heat, urine is clear; in interior heat, urine is red. For exterior heat with no sweating, Mahuang Tang (Ephedra Decoction) is indicated; if there is sweating, Guizhi Tang (Cinnamon Twig Decoction) is indicated. For mild cases of interior heat, Liangge San (Cool the Diaphragm Powder) is indicated; for severe cases, the Three Chengqi Decoctions (Da Chengqi Tang, Xiao Chengqi Tang, Tiaowei Chengqi Tang) are indicated. Fever accompanied by dry mouth, dry tongue, restlessness, and thirst indicates heat in the Yang meridians, which is true heat (Zhen Re); Baihu Tang (White Tiger Decoction) and similar formulas are indicated. Fever accompanied by cold extremities (Jue Leng) and diarrhea with undigested food (Xiali Qinggu) indicates heat in the Yin meridians, which is false heat (Jia Re); Sini Tang (Frigid Extremities Decoction) and similar formulas are indicated.
Fever accompanied by aversion to cold (E Han) originates in the Yang exterior. If there is sweating, Guizhi Tang (Cinnamon Twig Decoction) is indicated; if there is no sweating, Mahuang Tang (Ephedra Decoction) is indicated. Absence of fever but presence of aversion to cold originates in the Yin interior. If there is sweating, Guizhi Jia Fuzi Tang (Cinnamon Twig Decoction plus Aconite) is indicated; if there is no sweating, Mahuang Fuzi Xixin Tang (Ephedra, Aconite, and Asarum Decoction) is indicated. Aversion to cold in the back, with a non-dry mouth and calm demeanor, belongs to Shaoyin disease; Fuzi Tang (Aconite Decoction) is indicated. Aversion to cold in the back, with a dry mouth and thirst, belongs to Yangming disease; Baihu Jia Renshen Tang (White Tiger Decoction plus Ginseng) is indicated.
Wind pathogen and Cold pathogen generally accompany each other and rarely separate. When there is cold, there is not necessarily no wind; when there is wind, there is not necessarily no cold. Therefore, aversion to cold (E Han) and aversion to wind (E Feng) often appear together in all three Yang meridians. Both aversion to wind and aversion to cold belong to exterior diseases, and the treatment principle should focus on releasing the exterior. However, wind belongs to Yang, and cold belongs to Yin; thus, in the syndromes of the three Yin meridians, there is aversion to cold but no aversion to wind.
Headache involving the three Yang meridians is accompanied by fever throughout the body; the treatment principle should address the three Yang meridians. If there is constipation and red urine, it indicates that interior heat has become solid; Chengqi Tang (Purgative Decoction) should be used to purge. If the urine is clear and white, even if there is constipation, it indicates that interior heat has not yet become solid and the exterior pathogen has not been cleared; the treatment principle should first address the exterior. Headache involving the Jueyin meridian is mostly characterized by cold extremities without fever, accompanied by vomiting of saliva and foam; this is due to Jueyin meridian carrying cold pathogen upward in rebellion; Wuzhuyu Tang (Evodia Decoction) is indicated to warm and descend. The three Yin meridians typically do not present with headache; only the Jueyin meridian presents with headache because its channel connects with the Du Mai (Governing Vessel) at the vertex. The three Yin meridians typically do not present with fever; however, Jueyin and Shaoyin may also present with fever, termed "counterfeit fever" (Fan Fa Re), because the Zang organs contain Ministerial Fire (Xiang Huo), and excessive Yin repels Yang to the exterior.