汗者心之液。心主营。寒伤营。则血凝泣而无汗。无汗则宜发汗矣。然同一无汗而受病
之因
有不同。宜审其邪之所在而善调之。使阴阳气和。营卫流通。自然汗出而解。而非纯用辛温
发散之剂。可以迫之使汗也。
太阳病宜以汗解。以太阳主表故也。然风寒暑湿热之邪。起自太阳者。往往多自汗出。
惟寒伤营则无汗。必大发其汗而始解。如经云。太阳病头痛发热。身疼腰痛。骨节疼痛。恶风无
汗而喘者。麻黄汤主之。又云。太阳中风脉浮紧。发热恶寒。身疼痛。不汗出而烦躁者。大
青龙汤主之。又云。太阳病项背强KT KT 。无汗。恶风者。葛根汤主之。此皆邪在表而宜发汗
者是也。
其有不从汗解而从衄解者。经云。太阳病脉浮紧发热身无汗。自衄者。愈。盖寒伤营。
营主血。得衄而解。与汗同义。即俗所称为红汗者是也。
其有病在阳明而无汗者。如经云。阳明病反无汗而小便利。二三日呕而咳。手足厥者。
必苦
头痛。又云。阳明病无汗。小便不利。心中懊 者。身必发黄。盖邪在于表。熏发腠理。则
使汗自出。故经云。病患 然汗出者。是转属阳明也。此则邪向内传。不外熏发。故无汗也
。
有阳虚而无汗者。经云。脉浮而迟。迟为无阳。不能作汗。其身必痒。又云。阳明病反
无汗
。其身如虫行皮中状者。此以久虚故也。是阳虚而无汗者也。有因阳热炽盛。阴液被夺。而
无汗者。经云。伤寒脉浮。发热无汗。其表不解者。不可与白虎汤。渴欲饮水。无表证者。
白虎加人参汤主之。盖有表证者。还宜治表。此则表证除而热渴炽盛。故宜以人参白虎急救
其阴。俾阴气和则阳热外越。自然汗出而解也。
三阴为病。不得有汗。以邪行于里故也。同一无汗而阴与阳又何以别之。盖阳脉主浮。
而阴脉必沉也。
又有水饮内蓄而无汗者。经云。服桂枝汤或下之。仍头项强痛。翕翕发热无汗心下满微
痛。
小便不利者。桂枝去桂加茯苓白术汤主之。盖汗者津液所布。今水饮内蓄。则津液内渗。故
外不得有汗也。
凡当汗之证。服汤一剂。病势仍在。至于服三剂而仍不得汗。又加以脉躁盛者主死。
汗是心所主管的体液。心主运行营气。寒邪损伤营分，导致血液凝滞不畅，从而出现无汗症状。出现无汗时，适宜采用发汗法治疗。然而，同样是“无汗”，其致病原因却有所不同。应当仔细辨别病邪所在的部位并妥善调理，使阴阳之气调和，营卫之气流通，自然就会出汗而病愈，而不是单纯使用辛温发散的药物来强行逼迫出汗。
太阳病适宜通过发汗来解除，因为太阳经主司体表防御。然而，风、寒、暑、湿、热等邪气，虽然起始于太阳经，往往多表现为自汗出。只有寒邪损伤营分时才会无汗，必须大力发汗才能解除。正如经典所说：太阳病，头痛发热，身体疼痛，腰痛，骨节疼痛，恶风且无汗而气喘的，用麻黄汤主治。又说：太阳中风证，脉象浮紧，发热恶寒，身体疼痛，不出汗且烦躁的，用大青龙汤主治。又说：太阳病，项背部僵硬拘急不舒，无汗，恶风的，用葛根汤主治。这些都属于病邪在体表，适宜发汗的情况。
还有不从发汗解表，而是从鼻衄（出血）途径解除的。经典说：太阳病，脉象浮紧，发热，身体无汗，如果自然发生鼻衄的，病就会痊愈。这是因为寒邪损伤营分，营分主血，通过衄血得以解除，这与发汗的道理相同，也就是俗称的“红汗”。
还有病在阳明经却无汗的情况。如经典说：阳明病反而无汗，小便通畅，两三天后出现呕吐兼咳嗽，手足厥冷的，必定伴有剧烈头痛。又说：阳明病无汗，小便不利，心中烦闷懊恼的，身体一定会发黄。这是因为邪气在体表，熏蒸腠理，会使汗液自然排出，所以经典说：病人濈然（连续不断）出汗的，这是病邪转属阳明的表现。此处则是邪气向内传变，不再向外熏蒸腠理，所以无汗。
有因阳气虚弱而无汗的情况。经典说：脉象浮而迟，迟脉代表阳气不足，不能化生汗液，身体必定发痒。又说：阳明病反而无汗，身体感觉像有虫子在皮肤中爬行一样，这是由于久病体虚所致。这就是阳虚导致的无汗。还有因阳热炽盛，阴液被耗夺而无汗的情况。经典说：伤寒脉浮，发热无汗，表证未解除的，不可给予白虎汤。如果口渴想喝水，且没有表证的，用白虎加人参汤主治。因为有表证时，仍宜治疗表证；此处则是表证已除，但热渴炽盛，所以适宜用人参白虎汤急救阴液，使阴气调和，则阳热外越，自然出汗而病愈。
三阴经发病，通常不会有汗，因为邪气行于体内。同样是“无汗”，阴证与阳证又该如何区别呢？大概阳证的脉象主浮，而阴证的脉象必沉。
还有因水饮内停蓄积而无汗的情况。经典说：服用桂枝汤或经过攻下治疗后，仍然头项强痛，微微发热，无汗，心下部满微痛，小便不利的，用桂枝去桂加茯苓白术汤主治。因为汗是由津液布散而成，现在水饮内停，津液内渗，所以外部无法出汗。
凡是应当发汗的证候，服用一剂药后，病情仍在；如果服用三剂后仍然不得汗，再加上脉象躁动旺盛的，主死症。
Sweat is the fluid of the Heart. The Heart governs Ying (Nutritive Qi). When Cold pathogen injures Ying, blood coagulates and flows sluggishly, resulting in anhidrosis (absence of sweating). In cases of anhidrosis, it is appropriate to employ diaphoresis (sweating therapy). However, although the symptom is uniformly "anhidrosis," the etiological factors differ. One must carefully examine the location of the pathogen and regulate it properly, so that Yin and Yang Qi harmonize, and Ying and Wei (Defensive) Qi circulate freely; sweat will naturally emerge, resolving the disease. It is not a matter of purely using acrid-warm dispersing agents to forcibly compel sweating.
Taiyang disease (Disease of the Taiyang Channel) should be resolved through diaphoresis because the Taiyang channel governs the exterior. However, pathogens such as Wind, Cold, Summerheat, Dampness, and Heat, though originating from the Taiyang, often present with spontaneous sweating. Only when Cold injures Ying does anhidrosis occur, requiring vigorous diaphoresis for resolution. As stated in the classics: "In Taiyang disease, if there is headache, fever, body pain, lumbar pain, joint pain, aversion to wind, anhidrosis, and wheezing, Mahuang Tang (Ephedra Decoction) is indicated." It also states: "In Taiyang Wind-stroke, if the pulse is floating and tight, with fever, aversion to cold, body pain, anhidrosis, and irritability, Da Qinglong Tang (Major Blue-Green Dragon Decoction) is indicated." Furthermore: "In Taiyang disease, if there is stiffness and rigidity of the nape and back, anhidrosis, and aversion to wind, Gegen Tang (Kudzu Decoction) is indicated." These are all cases where the pathogen is at the exterior and diaphoresis is appropriate.
There are cases where resolution occurs not through sweating but through epistaxis (nosebleed). The classics state: "In Taiyang disease, if the pulse is floating and tight, with fever and anhidrosis, spontaneous epistaxis leads to recovery." This is because Cold injures Ying, which governs Blood; resolution via epistaxis shares the same principle as diaphoresis, commonly referred to as "Red Sweat."
There are cases of anhidrosis associated with Yangming disease. For instance: "In Yangming disease, if there is paradoxical anhidrosis, free urination, vomiting and coughing after two or three days, and cold extremities, severe headache must be endured." Also: "In Yangming disease, if there is anhidrosis, obstructed urination, and mental restlessness/oppresion (Ao Nao), jaundice will inevitably develop." This is because when the pathogen is at the exterior, it steams and diffuses the Cou Li (pores/skin interstices), causing natural sweating. Thus, the classics state: "If a patient sweats continuously (Ji Ran), the disease is transferring to Yangming." In the current context, however, the pathogen has transmitted inward and no longer steams the exterior, hence the absence of sweat.
There are cases of anhidrosis due to Yang deficiency. The classics state: "If the pulse is floating and slow, 'slow' indicates lack of Yang, inability to produce sweat, and the body will likely itch." Also: "In Yangming disease, if there is paradoxical anhidrosis and the body feels as if insects are crawling under the skin, this is due to chronic deficiency." This constitutes anhidrosis caused by Yang deficiency. There are also cases of anhidrosis due to excessive Yang-Heat consuming Yin fluids. The classics state: "In Shanghan (Cold Damage), if the pulse is floating, with fever and anhidrosis, and the exterior pattern remains unresolved, Baihu Tang (White Tiger Decoction) must not be given. If there is thirst desire to drink water, and no exterior pattern exists, Baihu Jia Renshen Tang (White Tiger Decoction plus Ginseng) is indicated." When an exterior pattern exists, treatment should focus on the exterior. Here, since the exterior pattern is resolved but heat and thirst are intense, it is appropriate to use Ren Shen Baihu Tang to urgently rescue Yin. Once Yin Qi harmonizes, Yang-Heat moves outward, and sweat emerges naturally, resolving the disease.
Diseases of the Three Yin channels generally do not present with sweating because the pathogen resides in the interior. Regarding how to distinguish Yin from Yang patterns despite both presenting with anhidrosis: generally, Yang patterns feature floating pulses, whereas Yin patterns feature sinking pulses.
There are also cases of anhidrosis due to internal retention of Water-Fluid. The classics state: "After taking Guizhi Tang (Cinnamon Twig Decoction) or undergoing purgation, if there remains stiffness and pain in the head and nape, slight fever, anhidrosis, fullness and mild pain in the epigastrium, and obstructed urination, Guizhi Qu Gui Jia Fuling Baizhu Tang (Guizhi Tang minus Cinnamon Twig plus Poria and Atractylodes Macrocephala Decoction) is indicated." Since sweat is distributed Jin-Ye (Body Fluids), and now Water-Fluid is retained internally, Jin-Ye infiltrates inward, preventing external sweating.
In all cases requiring diaphoresis, if one dose of decoction fails to alter the condition, and after three doses sweating still does not occur, accompanied by a rapid and turbulent pulse, death is indicated.