《内经》云∶五脏六腑皆令人嗽，不独肺也。此言咳嗽主肺，然别经亦有之，于是详列十二经
络主咳症形以治内伤。至《伤寒论》太阳篇，论咳两条，皆曰心下有水气，皆用小青龙汤。此
以水饮内伏，心下太阳表症未解，用发散心下水饮主治。其少阳篇云∶咳者，小柴胡汤。此
以邪传少阳主治。其少阳篇两条，一以小便不利，泄利下重，用四逆散；一以下利六七日，
咳而呕渴，心烦不得眠，用猪苓汤。二者皆阳邪传入阴经，当以湿热主治。《伤寒论》惟有太
阳少阳少阴三经致嗽，非《内经》详而仲景略也。盖因内伤门咳嗽者多，外感咳嗽者少。然外
感者，六气皆能致也。伤寒致咳，恶寒身痛，发热无汗，脉浮紧，肺素无热，外受寒邪，未
经郁热，冬月可用三拗汤。肺热感寒者，羌防泻白散。伤风致咳，头痛额痛，发热多汗，脉
浮而缓，荆防饮。以上二条，表邪利害，宜散表。伤热致咳，喉痛声哑，不恶寒反恶热，汗
出而热，脉沉而数，黄芩泻白散加荆芥、薄荷；兼风者，加防风。伤燥致咳，口渴唇焦，内
热烦躁，时常有汗，干嗽无痰，连嗽不已，时或停止，遇夜益甚，右脉急数，泻白散加石
膏、黄芩。风湿致咳，泻白散合防风神术汤。大凡外感咳逆，既明何经主病，又当究何气致
病，因寒散寒，因风散风，有热清热，有湿利湿，必当去其致病之根。以外感咳嗽，但去病
邪，正气自复。例如热病，初起不咳，后致咳，皆因热邪伏于肺胃，要先清其所伏之热邪。
是以外感之嗽，初起即当从外散表。若初起先见咳嗽，即为肺家受邪，单治肺邪。若见左胁
作痛，即为金邪入木，以肺受邪热，乘克少阳肝胆木位，宜清理肺邪，佐以清肝胆之药，如
泻白散加柴胡、黄芩，以清少阳。惟先见少阳寒热症，后变咳嗽，乃名木火刑金，以少阳火
邪刑伤肺金而为咳嗽，宜清少阳，佐以清肺之药，如泻清各半汤等，加桑白皮、桔梗。
伤寒表不解，心下有水气，干呕发热而喘咳，或渴，或利，或噎，或小便不利，小腹满，或
喘者，小青龙汤主之。
此言外有太阳表邪，内有水饮伏结，上则干呕发喘咳，下则小便不利，小腹满，故以小青
龙汤辛散内伏之水饮，敷布胃中，从发表之药作汗外解。
伤寒心下有水气，咳而微喘，发热不渴，服汤已渴者，此寒去欲解也。小青龙汤主之。
此重申太阳经，心下有水气喘咳，发热不渴，可用小青龙汤。服小青龙汤已发渴者，此寒
饮已去，病欲解，不必再服小青龙汤。
小青龙汤
麻黄 桂枝 白芍药 干姜 细辛 五味子 半夏 甘草
此方泛视杂合，细玩有苦心。原文云∶伤寒表不解，心下有水气，干呕发热而咳。又云∶
心下有水气，咳而微喘，发热不渴。皆以小青龙汤主之。曰表不解，不得不用麻、桂；曰
水气内伏，又非麻黄桂枝大青龙三方所能治。故以干姜、半夏辛散心下所伏之水饮，先散
中焦，续得麻桂、细辛引拔水引，作汗出表，不使水邪干肺喘咳。又以白芍药敛住肝家营
血，五味子敛住肾家阴津。但欲辛散心下内伏水饮，作汗发出皮毛，内散水饮，外解表
邪，不欲其阳液阴津，亦从麻、桂、细辛而出。夫大青龙汤，行周天之云雨；小青龙，地
下之蛟龙。初起但发山中内伏之水而外出，若不用干姜、半夏先散水饮，徒用麻、桂散
表，则伏内之水饮不散。若用十枣汤等下水饮，太阳之表邪，乘虚内陷。
小柴胡汤 见寒热。
小柴胡去半夏加栝蒌根汤
同一少阳病，有呕吐，加半夏；有烦渴，去半夏，易以栝蒌根。
荆防饮
荆芥 防风 桔梗 甘草 桑白皮 杏仁
此方治伤风咳嗽，用桔梗开肺窍，桑白皮、杏仁泻肺气，加荆芥、防风将肺中之风轻轻泻药出。
黄芩泻白散
桑白皮 地骨皮 甘草 黄芩
三拗汤，治肺受寒邪而嗽者，荆防饮，治肺受风邪而嗽者；此方治肺火嗽者。广而推之，
燥火加知母、石膏；风热加防风、石膏；风湿加防风、苍术；痰多者加栝蒌、海石。
《黄帝内经》说：五脏六腑的病变都能导致咳嗽，并不仅仅是肺脏的问题。这句话虽然指出咳嗽主要与肺有关，但其他经络也会引起咳嗽，因此详细列举了十二经络主司咳嗽的症状表现以治疗内伤引起的咳嗽。到了《伤寒论》的太阳篇，论述咳嗽的条文有两条，都说是心下有停饮（水液代谢障碍形成的病理产物），都使用小青龙汤治疗。这是针对水饮内伏、心下太阳表证未解的情况，用发散的方法治疗心下的水饮。其少阳篇说：出现咳嗽症状的，用小柴胡汤治疗。这是针对邪气传入少阳的情况进行治疗。其少阳篇的两条内容中，一条因小便不利、泄泻且肛门重坠感，使用四逆散；另一条因腹泻六七天，伴有咳嗽、呕吐、口渴、心烦不得眠，使用猪苓汤。这两种情况都是阳热邪气传入阴经，应当以清热利湿的方法治疗。《伤寒论》中只有太阳、少阳、少阴三经导致咳嗽，并不是《内经》论述详尽而张仲景论述简略。大概是因为内伤门中的咳嗽患者较多，外感引起的咳嗽较少。然而外感咳嗽，六淫之气都能导致。
伤寒导致的咳嗽，表现为恶寒、身体疼痛、发热、无汗、脉象浮紧，肺部原本没有热邪，是外受寒邪，尚未郁结化热，冬季可以使用三拗汤。如果是肺热又感受寒邪，使用羌防泻白散。伤风导致的咳嗽，表现为头痛、额痛、发热、多汗、脉象浮而缓，使用荆防饮。以上两种情况，表邪较为严重，适宜疏散表邪。伤热导致的咳嗽，表现为咽喉肿痛、声音嘶哑、不恶寒反而怕热、出汗且发热、脉象沉而数，使用黄芩泻白散加荆芥、薄荷；兼有风邪的，加防风。伤燥导致的咳嗽，表现为口渴、嘴唇焦裂、内热烦躁、时常有汗、干咳无痰、连续咳嗽不止、有时停止、夜间加重、右脉急数，使用泻白散加石膏、黄芩。风湿导致的咳嗽，使用泻白散合防风神术汤。大凡外感引起的咳逆，既然明确了是哪条经络的主病，又应当探究是什么邪气致病，因寒则散寒，因风则散风，有热则清热，有湿则利湿，必须去除致病的根源。因为外感咳嗽，只要去除了病邪，正气自然恢复。例如热病，初起时不咳嗽，后来导致咳嗽，都是因为热邪潜伏在肺胃，要先清除潜伏的热邪。所以外感引起的咳嗽，初起就应当从外部疏散表邪。如果初起先见到咳嗽，就是肺脏受到邪气侵袭，单独治疗肺部的邪气。如果见到左胁作痛，就是金邪入木（肺金之邪侵犯肝木），因为肺受邪热，乘克少阳肝胆木位，宜清理肺邪，佐以清肝胆的药物，如泻白散加柴胡、黄芩，以清少阳。只有先见少阳寒热症状，后来变为咳嗽，才名叫木火刑金（肝胆之火灼伤肺金），因为少阳火邪刑伤肺金而导致咳嗽，宜清少阳，佐以清肺的药物，如泻清各半汤等，加桑白皮、桔梗。
伤寒表证未解，心下有停饮，干呕、发热而喘咳，或者口渴，或者腹泻，或者噎塞，或者小便不利、小腹胀满，或者气喘的，以小青龙汤主治。
这是说外有太阳表邪，内有水饮伏结，上则干呕发喘咳，下则小便不利、小腹胀满，所以用小青龙汤辛温发散内伏的水饮，敷布于胃中，随着发表药物化作汗液向外解除。
伤寒心下有停饮，咳嗽且轻微气喘，发热但不口渴，服药后感到口渴的，这是寒气去除、病情将要解除的表现。用小青龙汤主治。
这是重申太阳经，心下有停饮导致气喘咳嗽，发热但不口渴，可用小青龙汤。服用小青龙汤后出现口渴的，这是寒饮已去，病欲解除，不必再服用小青龙汤。
小青龙汤
麻黄 桂枝 白芍药 干姜 细辛 五味子 半夏 甘草
这个方子看似杂乱混合，仔细玩味则有苦心。原文说：伤寒表证未解，心下有停饮，干呕发热而咳。又说：心下有停饮，咳嗽且轻微气喘，发热但不口渴。都用小青龙汤主治。说“表不解”，不得不使用麻黄、桂枝；说“水气内伏”，又不是麻黄汤、桂枝汤、大青龙汤三方所能治疗的。所以用干姜、半夏辛温发散心下所伏的水饮，先散中焦，接着借助麻黄、桂枝、细辛引导拔出水饮，化作汗出体表，不让水邪干扰肺部导致喘咳。又用白芍药收敛肝家的营血，五味子收敛肾家的阴津。只是想要辛温发散心下内伏的水饮，化作汗液发出皮毛，内散水饮，外解表邪，不希望阳气津液也随着麻黄、桂枝、细辛而出。大青龙汤，运行周天的云雨；小青龙汤，如同地下的蛟龙。初起只发散山中内伏的水饮而外出，如果不用干姜、半夏先散水饮，徒用麻黄、桂枝发散表邪，那么内伏的水饮就不能消散。如果使用十枣汤等攻下水饮，太阳的表邪就会乘虚内陷。
小柴胡汤 见寒热章节。
小柴胡去半夏加栝蒌根汤
同样是少阳病，有呕吐症状的，加半夏；有烦渴症状的，去掉半夏，改用栝蒌根。
荆防饮
荆芥 防风 桔梗 甘草 桑白皮 杏仁
这个方子治疗伤风咳嗽，用桔梗开宣肺窍，桑白皮、杏仁泻肺气，加荆芥、防风将肺中的风邪轻轻泻出。
三拗汤，治疗肺受寒邪而咳嗽的；荆防饮，治疗肺受风邪而咳嗽的；此方（黄芩泻白散）治疗肺火咳嗽的。推广开来，燥火加知母、石膏；风热加防风、石膏；风湿加防风、苍术；痰多的加栝蒌、海浮石。
The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "Diseases of the five zang organs and six fu organs can all cause coughing; it is not solely due to the Lung." This statement indicates that while coughing is primarily associated with the Lung, other meridians can also induce coughing. Therefore, the manifestations of coughing governed by the twelve meridians are detailed to treat internal injury-induced coughing. In the Taiyang chapter of the *Shanghan Lun* (Treatise on Cold Damage), there are two clauses discussing coughing, both stating that there is "water qi in the epigastrium" (pathological fluid retention in the stomach area), and both prescribe Xiao Qing Long Tang (Minor Blue Dragon Decoction). This treatment addresses water-fluid retention internally and unresolved Taiyang exterior syndrome at the epigastrium, using dispersing methods to resolve the water-fluid in the epigastrium. The Shaoyang chapter states: "For those presenting with coughing, use Xiao Chai Hu Tang (Minor Bupleurum Decoction)." This treats conditions where pathogenic factors have transmitted to the Shaoyang meridian. Two clauses in the Shaoyang chapter mention: one uses Si Ni San (Frigid Extremities Powder) for cases with ineffective urination, diarrhea, and a sensation of heaviness in the anus; the other uses Zhu Ling Tang (Polyporus Decoction) for cases with diarrhea lasting six or seven days, accompanied by coughing, vomiting, thirst, irritability, and inability to sleep. Both scenarios involve yang pathogens transmitting to yin meridians and should be treated with clearing heat and promoting diuresis to remove dampness. The *Shanghan Lun* only mentions coughing caused by the Taiyang, Shaoyang, and Shaoyin meridians; this is not because the *Neijing* was detailed while Zhang Zhongjing was brief. It is likely because coughs due to internal injuries are more common than those due to external contractions. However, external contraction coughs can be caused by any of the six climatic factors (Six Qi).
Coughs caused by Cold Damage present with aversion to cold, body pain, fever, absence of sweating, and a floating-tight pulse. If the lungs originally lack heat and the condition results from external cold invasion without yet stagnating into heat, San Ao Tang (Three Unbinding Decoction) may be used in winter. For cases where lung heat is combined with cold invasion, Qiang Fang Xie Bai San (Saussurea and Saposhnikovia Decoction to Drain the White) is used. Coughs caused by Wind Injury present with headache, frontal pain, fever, profuse sweating, and a floating-slow pulse; Jing Fang Yin (Notopterygium and Saposhnikovia Infusion) is indicated. In the above two cases, where exterior pathogens are severe, dispersing the exterior is appropriate. Coughs caused by Heat Injury present with sore throat, hoarseness, aversion to heat rather than cold, sweating with fever, and a deep-rapid pulse; Huang Qin Xie Bai San (Scutellaria Decoction to Drain the White) added with Jing Jie (Schizonepeta Herb) and Bo He (Mentha Herb) is used. If wind is also present, Fang Feng (Saposhnikovia Root) is added. Coughs caused by Dryness Injury present with thirst, cracked lips, internal heat and irritability, occasional sweating, dry cough without phlegm, continuous coughing that sometimes stops, worsening at night, and an urgent-rapid right pulse; Xie Bai San (Draining White Powder) added with Shi Gao (Gypsum Fibrosum) and Huang Qin (Scutellaria Root) is used. Coughs caused by Wind-Dampness are treated with Xie Bai San combined with Fang Feng Shen Zhu Tang (Notopterygium and Atractylodes Macrocephala Decoction). Generally, for externally contracted coughing, after determining which meridian is primarily affected, one must investigate the specific pathogenic factor causing the disease: disperse cold if cold is present, disperse wind if wind is present, clear heat if heat is present, and promote diuresis to remove dampness if dampness is present. It is essential to eliminate the root cause of the disease. Since external contraction coughs result from pathogenic factors, removing the pathogen allows the healthy qi to recover naturally. For example, in febrile diseases, if coughing does not appear initially but develops later, it is because heat pathogens have hidden in the lungs and stomach; thus, the hidden heat pathogens must be cleared first. Therefore, externally contracted coughs should be treated by dispersing the exterior from the onset. If coughing appears immediately at the onset, it indicates the Lung has been invaded by pathogens, and treatment should focus solely on the Lung pathogens. If left hypochondriac pain is observed, it indicates Metal invading Wood (Lung metal pathology affecting Liver/Gallbladder wood); since the Lung is affected by heat pathogens that overcome the Shaoyang Liver-Gallbladder Wood position, one should clear Lung pathogens and assist with herbs that clear the Liver and Gallbladder, such as Xie Bai San added with Chai Hu (Bupleurum Root) and Huang Qin, to clear the Shaoyang. Only when Shaoyang chills and fever symptoms appear first and subsequently transform into coughing is it termed "Wood Fire Punishing Metal" (Liver/Gallbladder fire damaging Lung metal); here, Shaoyang should be cleared, assisted with herbs that clear the Lung, such as Xie Qing Ge Ban Tang (Half-Half Decoction of Draining White and Clearing Shaoyang) added with Sang Bai Pi (Morus Root Bark) and Jie Geng (Platycodon Root).
In Cold Damage, if the exterior syndrome is unresolved and there is water qi in the epigastrium, presenting with dry retching, fever, wheezing, and coughing, or possibly thirst, diarrhea, choking sensation, ineffective urination, lower abdominal fullness, or wheezing alone, Xiao Qing Long Tang (Minor Blue Dragon Decoction) is the primary treatment.
This describes having Taiyang exterior pathogens externally and water-fluid retention internally. Upward, it causes dry retching, wheezing, and coughing; downward, it causes ineffective urination and lower abdominal fullness. Thus, Xiao Qing Long Tang is used to acridly disperse the internally retained water-fluids, distributing them in the stomach, and resolving them through sweating via exterior-dispersing properties.
In Cold Damage, if there is water qi in the epigastrium, presenting with coughing and slight wheezing, fever but no thirst, and the patient becomes thirsty after taking medicine, this indicates the cold is departing and the disease is about to resolve. Xiao Qing Long Tang (Minor Blue Dragon Decoction) is the primary treatment.
This reiterates the Taiyang meridian condition: water qi in the epigastrium causing wheezing and coughing, with fever but no thirst, making Xiao Qing Long Tang applicable. If the patient becomes thirsty after taking Xiao Qing Long Tang, it indicates the cold-fluid has been eliminated and the disease is resolving; therefore, Xiao Qing Long Tang need not be taken again.
Xiao Qing Long Tang (Minor Blue Dragon Decoction)
Ephedrae Herba (Mahuang, 麻黄)
Cinnamomi Ramulus (Guizhi, 桂枝)
Paeoniae Radix Alba (Baishao Yao, 白芍药)
Zingiberis Rhizoma Recens (Ganjiang, 干姜)
Asari Radix et Rhizoma (Xixin, 细辛)
Schisandrae Fructus (Wuweizi, 五味子)
Pinelliae Rhizoma Preparatum (Banxia, 半夏)
Glycyrrhizae Radix et Rhizoma (Gancao, 甘草)
This formula appears mixed at first glance, but careful study reveals its profound logic. The original text states: "Cold Damage with unresolved exterior and water qi in the epigastrium, causing dry retching, fever, and coughing." It also states: "Water qi in the epigastrium, causing coughing and slight wheezing, with fever but no thirst." Both are treated with Xiao Qing Long Tang. Because the "exterior is unresolved," Mahuang and Guizhi are indispensable. Because "water qi is retained internally," the formulas Mahuang Tang, Guizhi Tang, and Da Qing Long Tang (Major Blue Dragon Decoction) are insufficient. Therefore, Ganjiang and Banxia are used to acridly disperse the water-fluids retained in the epigastrium, first dispersing the middle jiao. Subsequently, Mahuang, Guizhi, and Xixin guide and extract the water-fluids, inducing sweating to release them from the exterior, preventing water pathogens from disturbing the lungs and causing wheezing and coughing. Baishao is used to astringe the Ying-blood of the Liver, and Wuweizi is used to astringe the Yin-fluids of the Kidney. The goal is to acridly disperse the internally retained water-fluids in the epigastrium, releasing them as sweat through the skin, dispersing water internally and resolving exterior pathogens externally, without allowing Yang fluids and Yin fluids to exit along with Mahuang, Guizhi, and Xixin. Da Qing Long Tang circulates clouds and rain throughout the universe; Xiao Qing Long Tang is like a dragon beneath the earth. At the onset, it only disperses the internally retained water in the mountains and releases it outward. If Ganjiang and Banxia are not used first to disperse the water-fluids, and only Mahuang and Guizhi are used to disperse the exterior, the internally retained water-fluids will not dissipate. If Shizao Tang (Ten Date Pill Decoction) or similar formulas are used to purge the water-fluids, the Taiyang exterior pathogens will sink inward due to the deficiency.
Xiao Chai Hu Tang (Minor Bupleurum Decoction) See section on Chills and Fever.
Xiao Chai Hu Tang minus Banxia plus Tian Hua Fen (Trichosanthes Root)
In the same Shaoyang disease, if there is vomiting, add Banxia; if there is irritability and thirst, remove Banxia and replace it with Tian Hua Fen.
Jing Fang Yin (Notopterygium and Saposhnikovia Infusion)
Schizonepetae Spica (Jingjie, 荆芥)
Saposhnikoviae Radix (Fangfeng, 防风)
Platycodi Radix (Jiegeng, 桔梗)
Glycyrrhizae Radix et Rhizoma (Gancao, 甘草)
Mori Cortex (Sangbaipi, 桑白皮)
Pruni Semen (Xingren, 杏仁)
This formula treats coughs caused by Wind Injury. Jiegeng opens the Lung orifices; Sangbaipi and Xingrin drain Lung Qi; Jingjie and Fangfeng gently expel wind from the Lungs.
Huang Qin Xie Bai San (Scutellaria Decoction to Drain the White)
Mori Cortex (Sangbaipi, 桑白皮)
Lycti Cortex (Digupi, 地骨皮)
Glycyrrhizae Radix et Rhizoma (Gancao, 甘草)
Scutellariae Radix (Huangqin, 黄芩)
San Ao Tang (Three Unbinding Decoction) treats coughs caused by Cold pathogens invading the Lungs; Jing Fang Yin treats coughs caused by Wind pathogens invading the Lungs; this formula (Huang Qin Xie Bai San) treats coughs caused by Lung Fire. Expanding upon this principle: for Dryness-Fire, add Zhi Mu (Anemarrhenae Rhizoma) and Shi Gao (Gypsum Fibrosum); for Wind-Heat, add Fang Feng (Saposhnikoviae Radix) and Shi Gao (Gypsum Fibrosum); for Wind-Dampness, add Fang Feng (Saposhnikoviae Radix) and Cang Zhu (Atractylodis Rhizoma); for excessive phlegm, add Gua Lou (Trichosanthis Fructus) and Hai Shi (Floatstone).