Many people find that cold exposure reliably triggers the same cluster of symptoms: sudden chills without sweating, headache, cough with copious thin frothy phlegm that won't clear, chest tightness, and sometimes wheezing so severe it prevents lying flat at night. Years of cough suppressants and cold remedies bring only temporary relief. In TCM, this recurring pattern has a precise diagnosis: Wai Han Li Yin (External Cold with Internal Fluid Retention, 外寒里饮) — and a 2,000-year-old formula designed exactly for it: Xiao Qing Long Tang, recorded by Zhang Zhongjing in the Shang Han Lun. (Xiao Qing Long Tang — available here)

I. Origins and Core Pathomechanism

Xiao Qing Long Tang first appears in the Taiyang Disease chapter of the Shang Han Lun: "In Cold damage where the exterior has not resolved, with water-qi below the heart, dry retching, fever and cough — or thirst, diarrhoea, choking, difficult urination with lower abdominal fullness, or wheezing — Xiao Qing Long Tang governs."

The name references the Azure Dragon of the East in Chinese cosmology — symbol of generating, warming power that disperses Cold and transforms Water. Unlike Da Qing Long Tang (for External Cold with Internal Heat), Xiao Qing Long Tang treats External Cold with Internal Fluid, with a gentler but precisely targeted action: releasing the exterior, warming the Lungs, and dissolving phlegm-fluid simultaneously.

The core mechanism: Wind-Cold constrains the body's surface, blocking the pores and Wei Qi. Internally, pre-existing phlegm-fluid (often from Spleen weakness or habitual cold intake) is activated by the external cold, rises to obstruct Lung Qi, and disrupts the Lung's descending and dispersing functions. The result is the classic double presentation: exterior cold signs (chills, no sweat, headache, body ache) alongside interior fluid signs (cough, wheezing, thin frothy phlegm, chest oppression). As the Nan Jing states: "Cold of the body and cold beverages damage the Lung" — addressing both simultaneously is the only effective treatment.

II. Formula Composition

Eight herbs, each precisely assigned:

The formula's elegance lies in its "disperse-and-consolidate" balance: Ma Huang + Gui Zhi release exterior Cold; Gan Jiang + Xi Xin warm and dissolve internal fluid; Ban Xia transforms phlegm; Bai Shao + Wu Wei Zi prevent over-dispersal from depleting Yin; Zhi Gan Cao harmonises everything. The classical formula song captures it: "Xiao Qing Long is most effective — Wind-Cold on the surface, fluid blocking the chest; Xi Xin, Ban Xia, Gan Cao, Wu Wei Zi; Jiang, Gui, Ma Huang, and Shao Yao together."

III. Who This Formula Suits

Core presentation (check 3 or more):

• Constitution: Yang-deficient or Cold-fluid constitution — chronically cold, easily chilled, prone to cough after cold exposure; pale swollen tongue with white slippery coating, floating tight or wiry slippery pulse
• Exterior signs: aversion to cold, no sweating, headache, body ache, nasal congestion with clear discharge, throat itch — worse in cold
• Interior fluid signs: cough and wheezing, thin frothy copious phlegm that is difficult to expectorate, chest oppression, dry retching, no thirst or preference for hot drinks
• Triggers: cold exposure, rain, cold wind, cold food; symptoms worsen in autumn and winter

Modern clinical applications:

• Respiratory: acute bronchitis, chronic bronchitis exacerbation, bronchial asthma, COPD acute phase — with cold-type cough, wheezing, thin phlegm
• ENT: allergic rhinitis, catarrhal otitis media — nasal congestion, sneezing, clear discharge, ear fullness worsened by cold
• Rheumatic: rheumatoid arthritis with cold joint pain, heaviness, aversion to cold and no sweating
• Other: chronic nephritis or heart failure oedema with Cold-fluid pattern (with modifications)

IV. Xiao Qing Long Tang Contraindications & Safety

This formula contains potent and potentially toxic herbs. Do not self-prescribe.

• Pregnancy — Xi Xin is toxic; Ma Huang is stimulating. Both are contraindicated in pregnancy.
• Heat-type wheezing — high fever, flared nostrils, agitation, rapid breathing; this formula will worsen heat conditions.
• Hypertension, heart disease, glaucoma — Ma Huang's ephedrine alkaloids raise blood pressure and heart rate; use only under strict practitioner supervision.
• Allergy to any ingredient.

Critical preparation rules: Ma Huang must be pre-decocted for 5–10 minutes and the foam skimmed off to reduce its intensity. Xi Xin must never exceed 6g — overdose causes lip numbness, dizziness, nausea, and limb weakness; stop immediately and seek medical attention if these occur. Use ceramic cookware only. Serve warm. Course: typically 3–7 days; stop when symptoms resolve. Avoid cold, raw, oily foods and alcohol during treatment.

V. Xiao Qing Long Tang Dosage & Common Clinical Modifications

As decoction: Pre-decoct Ma Huang, skim foam; add remaining herbs with 600ml water, soak 30 min, boil then simmer 20–30 min to ~300ml; strain and take warm in two doses, 30 min after meals. Patent granule/liquid form (Xiao Qing Long Keli, Xiao Qing Long He Ji): follow package instructions, typically 1 sachet (13g) three times daily.

Common modifications (practitioner-directed only):

• Severe cough with heavy phlegm: add Xing Ren, She Gan, Kuan Dong Hua
• Cold-fluid transforming to heat (irritability, thirst): add Sheng Shi Gao, Huang Qin
• Allergic rhinitis with prominent nasal symptoms: add Xin Yi, Cang Er Zi
• Marked oedema, poor urination: add Fu Ling, Zhu Ling, Ze Xie
• Prominent nausea/vomiting: increase Ban Xia, add Chen Pi
• Qi and body deficiency: reduce Ma Huang, add Huang Qi, Dang Shen

VI. Xiao Qing Long Tang Clinical Case Reference

Patient: Female, 58, chronic bronchitis for 5 years, recurring each autumn/winter after cold exposure. Recent episode (1 week): chills, no sweating, headache, cough and wheezing, copious thin frothy phlegm, chest oppression, dry retching, no thirst. Pale swollen tongue, white slippery coating, floating tight pulse. Multiple courses of cough syrup and cold medicine had failed.

Diagnosis: External Cold with Internal Fluid Retention (chronic bronchitis acute exacerbation).

Treatment: Xiao Qing Long Tang modified — Ma Huang 9g (pre-decocted), Gui Zhi 9g, Bai Shao 12g, Xi Xin 3g, Gan Jiang 6g, Ban Xia 12g, Wu Wei Zi 9g, Zhi Gan Cao 6g, plus Xing Ren 10g and She Gan 9g. One decoction daily, warm after meals.

Outcome: After 3 doses, chills, headache, and wheezing reduced significantly; phlegm volume decreased. At second visit, Ma Huang reduced to 6g, Fu Ling 15g added; continued 7 days. At third visit, all symptoms resolved, tongue coating normalised. Formula changed to Yu Ping Feng San for 1 week to consolidate. Follow-up: no cold-triggered bronchitis recurrence the following autumn.

Conclusion

Xiao Qing Long Tang is a classic formula in traditional chinese medicine used to treat exterior wind-cold attack combined with exterior cold with interior fluid retention. It releases the exterior, warms the lungs, transforms phlegm, and calms wheezing, making it highly effective for respiratory health issues involving watery phlegm and internal fluid retention.

Clinically, it is indicated for symptoms such as aversion to cold, absence of sweating, nasal congestion, body aches, dry retching, and wheezing. The formula contains key herbs including ma huang, gui zhi, xi xin, gan jiang, ban xia, wu wei zi, and bai shao. Wu wei zi helps nourishes blood and astringes yin, while the overall combination supports lung qi.

In modern practice, xiao qing long tang is often used for allergic rhinitis, chronic bronchitis, and certain cases of pneumonia with prominent cold and fluid retention patterns.

Xiao Qing Long Tang's "disperse and consolidate" design — releasing exterior Cold while warming and dissolving interior fluid, all without damaging Yin — makes it uniquely effective for cold-triggered respiratory conditions. Its nearly 2,000-year clinical record confirms its precision. However, its potent ingredients (especially Xi Xin and Ma Huang) require careful dosing and pattern confirmation. Always use under the guidance of a licensed TCM practitioner. Those with External Cold with Internal Fluid constitution should also support treatment with dietary warmth, adequate rest, and protection from cold.