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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).