热邪在中、上二焦则口苦，非特时疫为然，即感风寒口苦，亦属少阳热证。如时疫当恶寒、发热，表证正盛
时，见口苦，即于发表诸药中倍加清热之品，轻则黄芩，重则知母，再重则石膏。不但三阳表证如此，即三阴里证
手足冷，恶寒，呕利，胸、腹满，不渴，证状似乎纯冷无热，而一兼口苦，即当于温燥药中加利热之品。如用半
夏、苍术、草果、浓朴，必加木通、苓、泽，甚至加知母、黄芩，本吴氏达原之义。
口苦为热证的据，每遇证状模糊，寒热莫辨，必借此以决之。至舌苔黄黑干燥，烦躁，热渴，闭结，又清下之
不可或缓者矣。
口苦、口甘同为热证，苦为燥热，在上、中二焦，多渴，属三阳；甘为湿热，在中、下二焦，多不渴，属三
阴。盖脾胃属土，稼穑作甘，土邪下涉肾位，水土相蒸，甘味上溢于口，多兼呕吐。人每误认胃寒，而用温中之
剂，不知湿热在于下焦，土能克水，温燥太过，肾水告竭，总不见热渴诸证，惟目不见物，渐至昏沉而死。
口甘一证，在诸证初起，犹可用温燥开导之品，而亦不宜过剂。在时疫必以清热为主，消痰为辅，或胸中停饮
太甚，亦不过加苍术、半夏而已，如二陈去甘草加姜汁炒山栀、姜汁炒黄连、竹茹、黄芩等类，为口甘要药，乌梅
更妙，酸能胜甘，盖五行克制，自然之理也。或四苓散加山栀亦得，然必以时疫之大势，为用药之权衡，斯可矣。
热邪位于中焦、上焦二处时会出现口苦，这不仅仅是时行疫病（具有传染性的流行病）如此，即使是感受风寒后出现口苦，也属于少阳经的热证。例如在时行疫病应当出现恶寒、发热，且表证正处于旺盛阶段时，如果见到口苦的症状，就应当在解表的药物中加倍加入清热的药物，病情轻的用黄芩，病情重的用知母，再重的用石膏。
不仅三阳经的表证是这样，即使是三阴经的里证，表现为手脚冰冷、怕冷、呕吐腹泻、胸腹部胀满、不口渴，症状看起来完全是寒冷而没有热象，但只要兼见口苦，就应当在温燥的药物中加入利热的药物。如使用半夏、苍术、草果、厚朴时，必须加入木通、茯苓、泽泻，甚至加入知母、黄芩，这是遵循吴又可氏达原饮的原意。
口苦是判断热证的依据，每当症状模糊不清，寒热难以辨别时，必定借此来决断。至于舌苔黄黑干燥、烦躁、热渴、便秘，又是清热攻下法不可延缓的情况了。
口苦和口甘都属于热证，口苦为燥热，位于上、中二焦，多伴有口渴，归属于三阳经；口甘为湿热，位于中、下二焦，多不伴有口渴，归属于三阴经。大概因为脾胃属土，土的特性是稼穑作甘（产生甜味），如果土邪向下波及肾的位置，水土相互蒸腾，甘味向上溢出口腔，多兼有呕吐。人们常常误认为是胃寒，而使用温中的药剂，却不知道湿热在于下焦，土能克水，如果温燥太过，会导致肾水枯竭，虽然总不见热渴等热证表现，但眼睛看不见东西，逐渐昏沉而死。
口甘这一证候，在诸种病症初起时，还可以使用温燥开导的药物，但也不宜过量。在时行疫病中必须以清热为主，消痰为辅，如果是胸中停饮太严重，也不过是加苍术、半夏罢了，如二陈汤去掉甘草，加入姜汁炒的山栀、姜汁炒的黄连、竹茹、黄芩等类药物，是治疗口甘的要药，乌梅更妙，酸味能胜甘味，这是五行相克的自然道理。或者四苓散加山栀也可以，但必须以时行疫病的整体大势，作为用药的权衡标准，这样就可以了。
When pathogenic heat resides in the Middle and Upper Jiao (Middle and Upper Burners), bitter taste in the mouth occurs. This is not only seen in epidemic febrile diseases (infectious epidemic diseases), but also when contracting wind-cold, a bitter taste in the mouth still belongs to the Shaoyang (Lesser Yang) heat syndrome. For instance, during an epidemic febrile disease, when chills and fever are present and the exterior syndrome is at its peak, if a bitter taste in the mouth is observed, one should double the dosage of heat-clearing herbs among the exterior-releasing formulas. For mild cases, use Huangqin (Scutellariae Radix); for severe cases, use Zhimu (Anemarrhenae Rhizoma); for even more severe cases, use Shigao (Gypsum Fibrosum).
This principle applies not only to the exterior syndromes of the Three Yang meridians, but also to the interior syndromes of the Three Yin meridians. If symptoms such as cold extremities, aversion to cold, vomiting and diarrhea, chest and abdominal fullness, and absence of thirst appear, seemingly indicating a pure cold condition without heat, the presence of a bitter taste in the mouth indicates that heat-clearing and draining herbs must be added to the warming and drying formulas. When using Banxia (Pinelliae Rhizoma), Cangzhu (Atractylodis Rhizoma), Caoguo (Tsao-ko Fruit), and Houpo (Magnoliae Officinalis Cortex), it is essential to add Mutong (Akebiae Caulis), Fuling (Poria), and Zexie (Alismatis Rhizoma), and even Zhimu (Anemarrhenae Rhizoma) and Huangqin (Scutellariae Radix). This follows the original intent of Wu又可's Da Yuan Yin (Reach the Origin Decoction).
A bitter taste in the mouth is a key indicator of heat syndromes. Whenever symptoms are ambiguous and difficult to distinguish between cold and heat, this sign is relied upon for diagnosis. Furthermore, yellow or black dry tongue coating, restlessness, thirst due to heat, and constipation indicate that heat-clearing and purging methods cannot be delayed.
Both bitter taste and sweet taste in the mouth belong to heat syndromes. Bitter taste results from dry heat located in the Upper and Middle Jiao, often accompanied by thirst, and is associated with the Three Yang meridians; sweet taste results from damp-heat located in the Middle and Lower Jiao, often without thirst, and is associated with the Three Yin meridians. The Spleen and Stomach belong to Earth, and Earth produces sweetness. If Earth pathogen descends to involve the Kidney position, the interaction between Water and Earth causes the sweet flavor to overflow into the mouth, often accompanied by vomiting. People often mistakenly diagnose this as Stomach Cold and use warming middle-jiao formulas, unaware that damp-heat resides in the Lower Jiao. Since Earth controls Water, excessive use of warming and drying agents will deplete Kidney Water. Although typical heat signs like thirst may not be apparent, vision loss may occur, leading gradually to coma and death.
For the initial stage of various diseases presenting with sweet taste in the mouth, warming and opening/dispersing agents can be used, but should not be overdosed. In epidemic febrile diseases, treatment must primarily focus on clearing heat, with resolving phlegm as secondary. If there is excessive fluid retention in the chest, adding Cangzhu (Atractylodis Rhizoma) and Banxia (Pinelliae Rhizoma) suffices. Formulas such as Er Chen Tang (Two-Cured Decoction) with Gancao (Glycyrrhizae Radix et Rhizoma) removed, plus Jiangzhi Chao Shanzhi (Gardeniae Fructus stir-fried with ginger juice), Jiangzhi Chao Huanglian (Coptidis Rhizoma stir-fried with ginger juice), Zhuru (Bambusae Caulis in Taeniam), and Huangqin (Scutellariae Radix) are essential medicines for treating sweet taste in the mouth. Wumei (Mume Fructus) is particularly effective, as sour flavor overcomes sweet flavor, following the natural principle of Five Elements mutual restriction. Alternatively, Siling San (Four-Poria Powder) with Shanzhi (Gardeniae Fructus) can be used. However, medication must always be weighed against the overall trend of the epidemic febrile disease.