柴胡 黄芩 人参 甘草 生姜 半夏 大枣
胸中烦而不呕。去半夏人参。加栝蒌实。渴者。去半夏。加人参。栝蒌。腹痛。去黄芩
。加芍药。胁下痞硬。去大枣。加牡蛎。心下悸。小便不利。去黄芩。加茯苓。不渴。外有微热
。去人参。加桂枝。温覆取微汗。咳者。去人参大枣生姜加五味子。干姜。
主往来寒热。胸胁若满。嘿嘿不欲饮食。心烦喜呕。身有微热。又曰。有柴胡症者。但
见一症
不可汗。不可下。但当以小柴胡汤和解而已。夫邪既内传。则变不可测。须迎而夺之。故以
柴胡
里。则气必上逆。故以半夏散逆气。生姜辅柴胡以和表。甘枣辅黄芩以和里。
邪气自表。未敛
虽聚。而气未逆。邪气欲渐实也。去人参者。恐其助热。去半夏者。以无逆气。加栝蒌实者
。专除烦热耳。 渴为津枯。半夏性燥。故去之。人参甘润。栝蒌苦坚。可以生津而止渴。
气不通畅。血不和调。则为腹痛。黄芩能滞气。故去之。芍药能和营。故加之。 痞则气
满。甘能满中故去大枣。硬则形坚。故加牡蛎。 悸而小便不利停水之候也去黄芩之苦坚助水。
加茯苓之淡渗行水。 不渴者。里自和。故去人参。微热者。表未解。故加桂枝。 咳为气
逆。故去参枣之补。肺欲收。酸收逆气者 。五味之能也。干姜辛温快气。固主散寒。亦司
火逆。故仲景不分寒热。每治咳症。必用此二物也。
俗医治伤寒。不分阴阳虚实。概用小柴胡汤。去人参。加清热消导之药。以为常法。盖
喜其
禁捧腹矣。夫小柴胡为少阳经。半表半里。和解之剂。苟未至此经。谓之引邪入室。既过此
经。谓之守株待兔。倘太阳之表热。及阳明之标热。岂此汤所能治乎。若夫阴寒假热。足冷
脉沉者。投以此汤。立致危殆矣。嗟乎。人命至重。冥报难逃。后之学人须详审经症。有是
疾。则用是方。万勿蹈此陋辙也。
若胸中烦闷但不呕吐，去掉半夏和人参，加入栝蒌实。口渴的，去掉半夏，加入人参和栝蒌。腹痛的，去掉黄芩，加入芍药。胁下痞塞硬满的，去掉大枣，加入牡蛎。心下悸动、小便不利的，去掉黄芩，加入茯苓。不渴且体表有轻微发热的，去掉人参，加入桂枝，覆盖衣被以取得微微汗出。咳嗽的，去掉人参、大枣、生姜，加入五味子和干姜。
本方主治往来寒热（恶寒与发热交替出现），胸胁部胀满不适，神情默默不欲饮食，心烦喜呕，身体有轻微发热。又说：凡是有小柴胡汤证候表现的，只要见到其中一个症状，就不可使用发汗法，也不可使用攻下法，只应当用小柴胡汤进行和解治疗。既然邪气已经内传，变化不可预测，必须迎头痛击以祛除病邪。因此用柴胡来透达半表半里之邪；邪入半表半里，气机必然上逆，所以用半夏来散降逆气；生姜辅助柴胡以调和表邪；甘草和大枣辅助黄芩以调和里热。
邪气从体表而来，尚未完全收敛聚集，但气机尚未上逆，这是邪气逐渐趋于实盛的表现。去掉人参，是担心它助长热势；去掉半夏，是因为没有逆气需要降逆；加入栝蒌实，是为了专门清除烦热。口渴是因为津液枯竭，半夏性燥，所以去掉它。人参味甘润，栝蒌味苦而能坚阴，可以生津止渴。
气机运行不畅，血液调和失常，就会发生腹痛。黄芩容易阻滞气机，所以去掉它。芍药能够调和营血，所以加入它。痞塞是由于气机壅满，甘味药物容易令人中焦满闷，所以去掉大枣。硬满则是形体坚实，所以加入牡蛎以软坚散结。
心悸且小便不利，是水饮停聚的征象。去掉黄芩的苦寒坚阴之性以免助水，加入茯苓的淡渗利湿之性以行水气。
不渴，说明里气自和，所以去掉人参。体表有微热，说明表邪未解，所以加入桂枝。
咳嗽是由于气机上逆，所以去掉人参、大枣的补益作用。肺脏喜欢收敛，酸味药物具有收敛逆气的作用，这是五味子的功效。干姜辛温，能快气散寒，固然是主要用来驱散寒邪，也能治理火逆之咳，所以张仲景不分寒热，凡是治疗咳嗽病症，必定使用这两味药。
世俗医生治疗伤寒，不分阴阳虚实，一概使用小柴胡汤，去掉人参，加入清热消导的药物，以此作为常规方法。这大概是因为喜欢让患者捧腹大笑罢了。小柴胡汤是少阳经半表半里和解的方剂。如果病邪还没有到达这一经，使用此方叫做引邪入室；如果病邪已经过了这一经，使用此方叫做守株待兔。如果是太阳经的表热，以及阳明经的标热，难道是这个汤所能治疗的吗？至于阴寒证出现的假热，足冷脉沉的患者，投以此汤，立刻会导致危殆。唉！人命至重，因果报应难逃，后世的学人必须详细审察经络证候，有这种病，就用这种方，千万不要重蹈这种浅陋的覆辙啊。
Chai Hu (Bupleuri Radix), Huang Qin (Scutellariae Radix), Ren Shen (Ginseng Radix et Rhizoma), Gan Cao (Glycyrrhizae Radix et Rhizoma), Sheng Jiang (Zingiberis Rhizoma Recens), Ban Xia (Pinelliae Rhizoma), Da Zao (Jujubae Fructus).
If there is vexation in the chest without vomiting, remove Ban Xia and Ren Shen, and add Gua Lou Shi (Trichosanthis Fructus). If there is thirst, remove Ban Xia, and add Ren Shen and Gua Lou. If there is abdominal pain, remove Huang Qin, and add Shao Yao (Paeoniae Radix Alba). If there is fullness and hardness under the hypochondrium, remove Da Zao, and add Mu Li (Ostreae Concha). If there is palpitation of the heart and difficulty in urination, remove Huang Qin, and add Fu Ling (Poria). If there is no thirst but a slight fever on the exterior, remove Ren Shen, and add Gui Zhi (Cinnamomi Ramulus); cover with warm blankets to induce a slight sweat. If there is coughing, remove Ren Shen, Da Zao, and Sheng Jiang, and add Wu Wei Zi (Schisandrae Fructus) and Gan Jiang (Zingiberis Rhizoma).
This formula primarily treats alternating chills and fever (Wang Lai Han Re - alternating aversion to cold and heat), fullness and distension in the chest and hypochondrium, silent desire not to eat, vexation with a tendency to vomit, and a slight fever on the body. It is also stated that for those presenting with Xiao Chai Hu Tang syndrome, if even one symptom is observed, sweating methods and purgative methods must not be used; instead, only Xiao Chai Hu Tang should be employed to harmonize. Since the pathogenic factor has already transmitted inward, its changes are unpredictable; one must intercept and defeat it. Therefore, Chai Hu is used to penetrate the half-exterior and half-interior level. When pathogens enter this level, Qi inevitably rebels upward, so Ban Xia is used to scatter rebellious Qi. Sheng Jiang assists Chai Hu to harmonize the exterior. Gan Cao and Da Zao assist Huang Qin to harmonize the interior.
When pathogens come from the exterior and have not yet fully gathered, but Qi has not yet rebelled, this indicates the pathogen is gradually becoming excess. Ren Shen is removed because it might aid heat. Ban Xia is removed because there is no rebellious Qi to descend. Gua Lou Shi is added specifically to clear vexation and heat. Thirst indicates dryness of fluids; since Ban Xia is drying in nature, it is removed. Ren Shen is sweet and moistening; Gua Lou is bitter and astringent, both capable of generating fluids and relieving thirst.
When Qi circulation is unsmooth and blood harmony is disrupted, abdominal pain occurs. Huang Qin can stagnate Qi, so it is removed. Shao Yao can harmonize Ying (Nutritive) Qi, so it is added. Fullness (Pi) results from Qi accumulation; since sweet flavors can cause central fullness, Da Zao is removed. Hardness implies solid form, so Mu Li is added to soften hardness.
Palpitation accompanied by difficult urination is a sign of water retention. The bitter-astringent property of Huang Qin is removed to avoid aiding water; the bland-draining property of Fu Ling is added to promote water metabolism.
No thirst indicates internal harmony, so Ren Shen is removed. Slight fever on the exterior indicates the exterior pathogen is unresolved, so Gui Zhi is added.
Coughing is due to rebellious Qi, so the tonifying effects of Ren Shen and Da Zao are removed. The Lung desires astringency; sour substances have the ability to astringe rebellious Qi, which is the function of Wu Wei Zi. Gan Jiang is acrid and warm, capable of moving Qi and dispersing cold; while primarily used to disperse cold, it also manages fire-rebellion coughs. Thus, Zhang Zhongjing did not distinguish between cold and heat when treating cough; he invariably used these two herbs.
Empirical physicians treating Shang Han (Cold Damage) often fail to differentiate Yin/Yang or deficiency/excess, indiscriminately using Xiao Chai Hu Tang, removing Ren Shen, and adding heat-clearing and digestion-promoting herbs as a routine method. This is likely done merely to elicit laughter from patients holding their bellies. Xiao Chai Hu Tang is a harmonizing agent for the Shaoyang channel, situated at the half-exterior and half-interior. If the pathogen has not yet reached this channel, using this formula is called "leading the thief into the house." If the pathogen has passed this channel, using this formula is called "waiting by the stump for a hare." Could this formula treat the exterior heat of the Taiyang channel or the marked heat of the Yangming channel? As for false heat caused by Yin-cold, characterized by cold feet and a deep pulse, administering this formula would immediately lead to critical danger. Alas! Human life is of utmost importance, and karmic retribution is inescapable. Future students must carefully examine the channel syndromes: if there is this disease, use this formula. Do not tread upon such shallow paths again.