（附口苦 口甘）
口渴一证。乃伤寒一大关键。不可不细心体察。凡风寒在表。邪在太阳。不言渴也。一
入阳
明。则不恶寒反恶热。口渐知渴矣。其有太阳病初起而即口渴者。温热之邪。自里出表。虽
见表证。邪不在表。故仲景云。太阳病发热而渴。不恶寒者为温病。又太阳中 者。其人汗
出恶寒身热而渴也。是不宜发汗。与风寒异治。至于湿温初起。湿未化热。口虽渴。却不能
饮。化热之后。始大渴引饮矣。故就口之渴与不渴。可以辨邪之表里。中之寒热。而即可以
渴之微甚。辨热之轻重。临证时首宜辨此。
凡阳热之证。一见口渴。即当泄热为主。至三阴证。如系本藏虚寒自病者。本无所为渴
也。
然阴病转阳。亦有发热而渴者。当与和调津液。不宜直折其热。缘阴盛阳微。口渴正阳回之
候
。泄热则转泻其阳矣其或阴液干涸燥渴转甚。则量与泄热之中。尤当佐以养阴生津。此为大
渴
引饮者立法。若口中虽渴而不欲饮。见水辄避者。即属真寒假热之候。其脉或沉细。或空大
。当以温剂引阳归根。则虚寒之状反着。倘误与寒凉。祸不旋踵矣。
霍乱后多见口渴之证。经云。霍乱头痛发热身疼痛。热多欲饮水者。五苓散主之。寒多
不用水者。理中丸主之。盖吐下之后。津液已伤。且阴病转阳。宜以理脾为主。使脾气散精。表
里并解。津液流通。而渴自止矣。切不可见渴投凉。反增其逆。且五苓散上升脾津。下通水道
。若太阳病不解。犯入膀胱之府。其人有表里证。渴欲饮水。水入则吐者。亦主此方。以白
饮和服方寸七。多服暖水汗出愈。若无太阳表证。而但脉浮发热。渴欲饮水。小便不利者。
五苓之温化。又所不宜。则宜猪苓汤化热通津。凡若此者。皆与治阳热之渴用甘寒者不同也
。
凡口渴多属里证。若热在经而不在里者。口虽渴。但欲漱水不欲咽。此欲作衄血及斑疹
之先兆。不可
遽用寒凉壅遏邪气。当审其病因而施解表之法。又凡诸渴证欲饮水者。但当少少与之。令胃
气和则愈。若饮水过多。恐增喘哕悸满诸变。不可不慎。
别有口苦者。乃邪热入于少阳。故仲景以口苦咽干为少阳病之提纲。至于口甘。内经称
为脾
瘅。由湿热郁蒸而成。宜扫除胸中陈腐之气。此二者口虽不渴。总属热证。辛温忌投矣。
（附口苦、口甘）
口渴这一证候，是伤寒病的一个关键要点，不可不细心体察。凡是风寒邪气在体表，病位在太阳经，通常不会出现口渴的症状。一旦邪气传入阳明经，患者就会不再怕冷反而怕热，口中逐渐感到口渴。有的患者在太阳病初起时就出现口渴，这是温热邪气从体内向外透发所致，虽然表现出表证，但邪气并不在体表，所以张仲景说：“太阳病发热且口渴，不怕冷的，属于温病。”还有中暍（中暑）的患者，表现为出汗、怕冷、身体发热且口渴，这种情况不宜使用发汗法，治疗原则与风寒不同。至于湿温病初起时，湿气尚未化热，口中虽然觉得渴，但却不想喝水；等到湿气化热之后，才会出现大渴且大量饮水的情况。因此，通过观察口中是否口渴以及口渴的程度，可以辨别邪气的表里位置和中焦的寒热性质，并据此判断热邪的轻重。临证时首先应当辨析这一点。
凡是阳热性质的证候，一旦出现口渴，就应当以清泄热邪为主要治法。到了三阴病阶段，如果是本脏虚寒导致的自发病症，本来是不会口渴的。然而，阴病转化为阳病时，也会出现发热且口渴的情况，此时应当调和津液，不宜直接折损其热势。因为阴盛阳微，口渴正是阳气回复的征象，如果清泄热邪，反而会耗伤阳气。如果是因为阴液干涸导致燥渴加剧，那么在清泄热邪的同时，尤其应当辅以滋养阴液、生津止渴的方法，这是针对大渴引饮者制定的法则。如果口中虽然觉得渴，却不想喝水，见到水就躲避，这属于真寒假热的征象。其脉象可能沉细，也可能空大，应当使用温剂引导阳气回归根本，这样虚寒的真面目就会显露出来。倘若误用寒凉药物，灾祸很快就会发生。
霍乱病后多见口渴的证候。《内经》说：“霍乱头痛、发热、身体疼痛，热多且想喝水的，用五苓散主治；寒多且不想喝水的，用理中丸主治。”这是因为呕吐和腹泻之后，津液已经受损，加上阴病转阳，适宜以调理脾胃为主，使脾气能够散布精微物质，表里之邪同时解除，津液流通，口渴自然停止。切不可一见口渴就投用寒凉药物，反而会增加病情逆乱。而且五苓散能上升脾之津液，下通水道。如果太阳病未解，邪气侵犯膀胱腑，患者既有表证又有里证，口渴想喝水，喝水后则呕吐，也主治此方。用白米汤送服方寸匕大小的药量，多喝暖水以助汗出而痊愈。如果没有太阳表证，只是脉浮、发热、口渴想喝水、小便不利，那么五苓散的温化作用就不适宜了，此时宜用猪苓汤来清热利湿、通调津液。像这样的情况，都与治疗阳热口渴所用的甘寒药物不同。
凡是口渴大多属于里证。如果热邪在经络而不在脏腑内部，口中虽然觉得渴，但只想含水漱口而不愿咽下，这是即将发生鼻衄（流鼻血）及斑疹的先兆，不可急于使用寒凉药物壅遏邪气，应当审察病因施以解表之法。另外，对于各种口渴想喝水的患者，只应当少量多次给予，令胃气调和即可痊愈。如果饮水过多，恐怕会增加气喘、呃逆、心悸、胀满等变证，不可不谨慎。
另有口苦的，是邪热侵入少阳经所致，所以张仲景将口苦、咽干作为少阳病的提纲证。至于口甘，《内经》称之为“脾瘅”，是由湿热郁蒸而成，适宜扫除胸中的陈腐之气。这两种情况虽然不口渴，但总属热证，忌用辛温药物。
(Attached: Bitter Taste in Mouth, Sweet Taste in Mouth)
Thirst is a critical key point in Shanghan (Cold Damage diseases) and must be carefully observed. When wind-cold pathogens are at the exterior, affecting the Taiyang channel, thirst is typically not mentioned. Once the pathogen enters the Yangming stage, the patient ceases to fear cold and instead fears heat, gradually experiencing thirst in the mouth. In cases where thirst appears immediately at the onset of a Taiyang disease, it indicates warm-heat pathogens emerging from the interior to the exterior; although exterior symptoms are present, the pathogen is not truly at the exterior. Thus, Zhang Zhongjing stated: "Taiyang disease with fever and thirst, without aversion to cold, is classified as Warm Disease." Additionally, patients suffering from Heatstroke (Zhong Shu) exhibit sweating, aversion to cold, body heat, and thirst; this condition is unsuitable for diaphoresis (sweating therapy) and requires treatment different from wind-cold. Regarding Damp-Warmth at its onset, when dampness has not yet transformed into heat, the mouth may feel dry but the patient cannot drink; only after dampness transforms into heat does severe thirst with an urge to drink large amounts occur. Therefore, by observing whether there is thirst and its severity, one can distinguish the location of the pathogen (exterior vs. interior) and the nature of the middle jiao (cold vs. heat), thereby assessing the intensity of the heat. This differentiation should be the primary focus during clinical practice.
For all Yang-heat syndromes, once thirst appears, the primary treatment should be to drain heat. In Yin syndromes (San Yin diseases), if the condition arises from intrinsic deficiency-cold of the organ itself, thirst naturally does not occur. However, when a Yin syndrome transforms into a Yang syndrome, fever accompanied by thirst may appear. In such cases, one should harmonize the fluids rather than directly suppress the heat. Since Yin excess and Yang deficiency are present, thirst is actually a sign of Yang recovery; draining heat would further deplete Yang. If dryness and thirst intensify due to the depletion of Yin fluids, while draining heat, one must especially assist with nourishing Yin and generating fluids. This principle applies to those with severe thirst and an urge to drink. Conversely, if the mouth feels dry but the patient refuses to drink or avoids water, this indicates a pattern of True Cold and False Heat. The pulse may be deep and fine or empty and large. One should use warming agents to guide Yang back to its root, revealing the true state of deficiency-cold. Mistakenly using cold-cooling herbs would lead to rapid disaster.
Thirst is commonly seen after Huoluan (Vomiting and Diarrhea). The Classics state: "Huoluan with headache, fever, and body pain; if heat predominates and the patient desires water, Wuling San (Five-Ingredient Poria Pill) is indicated. If cold predominates and the patient does not desire water, Lizhong Wan (Regulate the Middle Pill) is indicated." This is because vomiting and purging damage the body fluids, and as Yin transforms to Yang, regulating the Spleen is appropriate to allow the Spleen Qi to distribute essence, resolving both exterior and interior aspects, circulating fluids, and stopping thirst. One must not blindly administer cooling herbs upon seeing thirst, as this may worsen the condition. Furthermore, Wuling San raises Spleen fluids and unblocks the water passages. If Taiyang disease remains unresolved and the pathogen invades the Bladder Fu organ, presenting with both exterior and interior symptoms, thirst, desire to drink, and vomiting after drinking, this formula is also indicated. It should be taken with rice water, one cun-bi dose, followed by warm water to induce sweating for cure. If there is no Taiyang exterior syndrome, but only floating pulse, fever, thirst, and difficult urination, the warming transformation of Wuling San is inappropriate; instead, Zhuling Tang (Polyporus Decoction) should be used to clear heat and regulate fluids. Such cases differ from treating Yang-heat thirst with sweet-cold herbs.
Generally, thirst belongs to interior syndromes. If heat is in the channels but not in the interior, the mouth may feel dry, but the patient only wishes to rinse their mouth with water without swallowing. This is a precursor to epistaxis (nosebleed) or maculopapular rashes. One should not hastily use cold-cooling herbs that might obstruct the pathogen; instead, analyze the cause and apply exterior-resolving methods. For various thirst conditions where the patient desires water, provide small amounts frequently until Stomach Qi harmonizes and the condition resolves. Excessive water intake may lead to complications such as asthma, hiccups, palpitations, and fullness; caution is essential.
Bitter taste in the mouth occurs when heat pathogens enter the Shaoyang channel; thus, Zhang Zhongjing lists bitter taste and dry throat as the guiding symptoms of Shaoyang disease. Sweet taste in the mouth is termed "Pi Dan" (Spleen Heat/Dampness) in the Inner Canon, caused by damp-heat stagnation and steaming. It is appropriate to clear stale qi from the chest. Although neither condition involves thirst, both belong to heat syndromes, and acrid-warm herbs are contraindicated.