Gua Lou (Trichosanthes Fruit, also written Gua Lou or Kua Lou; the dried ripe fruit of Trichosanthes kirilowii or T. rosthornii) is the most pharmacologically versatile herb in the TCM Phlegm-Heat clearing category. Its defining character: the entire fruit, the skin (Gua Lou Pi), and the seeds (Gua Lou Ren) are all separately pharmacopoeial-grade drugs with clearly distinct functional emphasis, which is exceptional even among multi-part herbs. TCM character: sweet, mildly bitter, cold; enters Lung, Stomach, and Large Intestine channels. The three-channel entry maps directly to three distinct clinical domains: Lung (clear Heat-Phlegm), chest-Stomach (relieve chest obstruction and scatter binding), Large Intestine (moisten Dryness and promote defecation). The Ben Cao Gang Mu comprehensive summary: “moistens Lung-Dryness, drains Fire, treats cough, washes away Phlegm-binding, benefits the throat, stops wasting-thirst, promotes defecation, dissolves carbuncle-sore toxins.” Zhang Zhongjing’s Jin Gui Yao Lue was the first to deploy Gua Lou clinically in the famous Gua Lou Xie Bai Ban Xia Tang for chest bi-obstruction, establishing its chest-opening action that remains in use nearly two millennia later.

I. Classical Records and Historical Significance

• Shen Nong Ben Cao Jing (middle-class, under Gua Lou / Gua Lou Gen): governs wasting-thirst, body Heat, vexation-fullness, severe Heat, supplements deficiency and settles the Middle — establishing the foundational clear-Heat, moisten-Dryness, relieve-thirst drug value
• Jin Gui Yao Lue (Zhang Zhongjing, Han dynasty): first clinical deployment of Gua Lou in Gua Lou Xie Bai Ban Xia Tang and related formulas; specifically for chest bi-obstruction with Phlegm-turbidity blocking the chest-Yang — establishing the chest-opening-and-Phlegm-scattering application that has been in continuous use since the Han dynasty
• Ben Cao Gang Mu: “moistens Lung-Dryness, drains Fire, treats cough, washes away Phlegm-binding, benefits the throat, stops wasting-thirst, promotes defecation, dissolves carbuncle-sore toxins” — the most comprehensive classical summary of Gua Lou’s five domains
• Chinese Pharmacopoeia: clear Heat and wash away Phlegm, broaden the chest and scatter binding, moisten Dryness and lubricate the intestines

II. TCM Properties, Three Parts and Identification

TCM properties: Sweet, mildly bitter, cold; enters Lung, Stomach, and Large Intestine channels. Drug character: clears and moistens, descends, does not violently attack. Cold clears Heat; bitter resolves Phlegm; sweet moistens Dryness. The three-channel entry provides Gua Lou with a top-to-bottom distribution of action: Lung (upper Jiao — clear Phlegm-Heat and stop cough), chest-Stomach (Middle Jiao — broaden the chest and scatter binding), Large Intestine (lower Jiao — moisten and promote defecation).

Regional origin and quality: Source: Trichosanthes kirilowii or T. rosthornii dried ripe fruit; primary production: Shandong, Henan, Hebei, Anhui; dao di: Shandong Feicheng Gua Lou and Henan Huai Gua Lou (large fruit, well-filled seeds, high oil content). Quality standard: large, complete, orange-red, thick flesh, no mould or insect damage.

The three pharmacopoeial parts — with distinct functional emphasis:

Core chemical constituents: Trichosanthes saponins; flavonoids; alkaloids; plant oils and fatty acids (the primary intestine-moistening laxative component); polysaccharides; amino acids. Saponins and flavonoids are the primary cardioprotective, expectorant, and anti-inflammatory components.

III. Five Core Actions

1. Clear Heat and wash away Phlegm — clear Lung and stop cough:
The primary Lung-channel action. Gua Lou’s cold nature clears Lung-Heat; its bitter quality resolves and washes away thick sticky Phlegm. Specifically targets: Heat-Phlegm and Dry-Phlegm cough — yellow thick sticky phlegm difficult to expectorate, throat dryness and itch, chest-diaphragm Heat-stuffiness, Lung-Heat dyspnoea. Clinical designation: “first-choice herb for Heat-Phlegm and Dry-Phlegm cough.” The pharmacological sequence: cold-clearing reduces Lung-Heat inflammation; bitter-resolving loosens the Phlegm-matrix; moist-flushing washes away the dissolved Phlegm. Modern pharmacology: inhibits airway inflammation, thins mucus (reducing viscosity), relaxes bronchial smooth muscle — directly supporting the expectorant and antitussive actions.

2. Broaden the chest and scatter binding — unblock chest-bi obstruction and settle pain:
Gua Lou’s most historically important action — the basis for Zhang Zhongjing’s Han dynasty formula design. Opens the chest-diaphragm Qi mechanism; dissolves Phlegm-turbidity and Qi-stagnation obstructing the chest-Yang; specifically treats: chest bi-obstruction producing chest stuffiness and oppression, shortness of breath, chest stabbing pain, chest-rib fullness and distension from Phlegm-turbidity blocking the chest-Yang. Modern pharmacology: dilates coronary arteries; improves myocardial blood supply; reduces vascular resistance; inhibits platelet aggregation — the molecular basis for the chest-opening action in cardiovascular disease.

3. Moisten Dryness and lubricate the intestines — promote defecation gently:
Gua Lou Ren’s oil-rich seeds lubricate the intestinal wall and promote peristalsis. This is the gentle oil-lubricating (run zao hua chang) laxative mechanism — distinct from bitter-cold purgation (Da Huang) or osmotic purging (Mang Xiao). Target pattern: intestinal-Dryness constipation from Lung-Stomach Dryness-Heat and fluid-Yin depletion producing dry-bound stool, difficult defecation, and straining without urgency. The simultaneous upper-lower action is unique: Gua Lou can clear Lung-Heat (addressing the root) while moistening intestines (addressing the manifestation) in the same prescription, because the same Dryness-Heat mechanism produces both the dry cough and the dry stool.

4. Reduce swelling and scatter binding — resolve carbuncle-sore toxins:
Clears Heat and disperses Stasis; dissolves Phlegm-Heat-toxin binding producing nodular accumulations. Addresses: breast carbuncle (ru yong) at initial onset with red swelling pain; Lung carbuncle (fei yong) with coughing purulent sputum; intestinal carbuncle (chang yong) abdominal pain; skin Hot-toxic sores and swellings; breast nodular masses. Modern pharmacology: anti-inflammatory and antibacterial actions; resolves inflammatory exudate — supports the sore-toxin dissolution action.

5. Generate fluids and relieve thirst, clear Heat and relieve vexation:
Clears Stomach-Heat and nourishes Stomach-fluid; improves: Dryness-Heat injuring fluids producing dry mouth and thirst, internal Heat wasting-thirst, copious drinking, vexing fullness from Lung-Stomach Heat exuberance. The Shen Nong Ben Cao Jing’s first-recorded action directly references this — “governing wasting-thirst, body Heat, vexation-fullness.”

IV. Clinical Applications

• Lung-Heat Phlegm-Heat cough: Wind-Heat and Lung-Heat cough with yellow thick sticky phlegm difficult to expectorate, throat-dryness and swelling-pain, dry mouth and Lung-Heat; for acute and chronic bronchitis, Lung-Heat Phlegm-copious respiratory conditions
• Chest bi-obstruction heart pain, chest stuffiness and fullness: Phlegm-turbidity obstructing the chest-Yang producing chest stuffiness and oppression, stabbing chest pain, shortness of breath, chest-diaphragm distension and fullness; adjunctive in coronary artery disease, chest stuffiness and shortness of breath, and chest-rib Qi-stagnation binding
• Lung-Dryness fluid-depletion, intestinal-Dryness constipation: autumn-winter dry-pathogen and internal Heat fluid-depletion producing dry cough with little phlegm, skin dryness, dry-bound stool, habitual intestinal-Dryness constipation; gentle fluid-generating and constipation-relieving without damaging constitutional Qi
• Various carbuncle-sore toxins: initial-onset breast carbuncle with red swelling pain; Lung carbuncle coughing purulent sputum; intestinal carbuncle abdominal pain; skin Hot-toxic sore swellings; clears Heat, scatters binding, dissolves swelling, and settles pain to promote resolution
• Internal Heat wasting-thirst, Dryness-Heat vexing fullness: Lung-Stomach Heat-exuberance and fluid-injury producing dry-excessive drinking, heart-vexation dryness-Heat, body vexing fullness; adjunctive in Dryness-Heat wasting-thirst

V. Five Classical Formulas

1. Gua Lou Xie Bai Ban Xia Tang “Trichosanthes-Allium-Pinellia Decoction” (Jin Gui Yao Lue)
Composition: Quan Gua Lou · Xie Bai · Ban Xia · Bai Jiu. Action: unblock Yang and scatter binding, dissolve Phlegm and broaden the chest. Indication: Phlegm-turbid chest bi-obstruction — chest stuffiness and heart pain, chest-diaphragm oppression, shortness of breath. The premier chest-opening formula in TCM; Gua Lou’s role: the primary Phlegm-dissolving and chest-broadening drug; Xie Bai unblocks Yang-Qi and disperses Cold-Phlegm; Ban Xia dissolves Phlegm and harmonises Stomach; Bai Jiu amplifies the Yang-unblocking force.

2. Qing Qi Hua Tan Wan “Clear Qi and Resolve Phlegm Pill”
Composition: Gua Lou Ren · Huang Qin · Ban Xia · Chen Pi · Xing Ren · Fu Ling. Action: clear Heat and resolve Phlegm, regulate Qi and stop cough. Indication: Phlegm-Heat cough — yellow thick sticky phlegm, chest-diaphragm stuffiness and fullness, coughing phlegm without ease. Gua Lou Ren’s role: clears and washes away sticky Phlegm; Huang Qin clears Lung-Heat; Ban Xia resolves Phlegm and harmonises; the combination powerfully addresses the dual Phlegm-and-Heat mechanism.

3. Xiao Xian Xiong Tang “Minor Sink-the-Chest Decoction” (Shang Han Lun)
Composition: Quan Gua Lou · Huang Lian · Ban Xia. Action: clear Heat and resolve Phlegm, scatter binding and open the stuffiness. Indication: Phlegm-Heat binding — chest-epigastric stuffiness and fullness, xin xia pi ying (epigastric hardness), pain on pressing. A three-herb formula of exceptional structural elegance: Gua Lou clears Heat-Phlegm and broadens the chest; Huang Lian clears Heat and drains Fire; Ban Xia dissolves Phlegm and scatters binding; together they address the Phlegm-and-Heat mutual-binding pattern that produces the epigastric hardness-on-pressure presentation.

4. Gua Lou Zhi Shi Tang “Trichosanthes-Immature Orange Decoction”
Composition: Gua Lou · Zhi Shi · Jie Geng · Xing Ren · Huang Qin. Action: clear Heat and resolve Phlegm, descend Qi and broaden the chest. Indication: Lung-Heat with Phlegm exuberance — cough with dyspnoea, copious Phlegm, chest-diaphragm distension and fullness. Gua Lou + Zhi Shi provide the Phlegm-clearing and chest-broadening; Jie Geng opens the Lung and expels Phlegm; Xing Ren descends Qi and stops cough; Huang Qin clears Lung-Heat.

5. Run Fei San “Moisten-Lung Powder”
Composition: Gua Lou Ren · Bei Mu · Xing Ren · Mai Dong. Action: moisten Lung and stop cough, generate fluids and moisten Dryness. Indication: Lung-Dryness dry cough, little sticky phlegm, dry-sore throat, fluid-Yin deficiency constipation. Gua Lou Ren’s seed-oil lubricates the Lung and intestines; Bei Mu dissolves Phlegm and scatters binding; Xing Ren descends Qi and moistens Dryness; Mai Dong nourishes Lung-Stomach Yin.

VI. Four-Herb Differential

VII. Modern Pharmacology

Core active constituents: Trichosanthes saponins (primary cardioprotective component); flavonoids; alkaloids; plant oils and fatty acids (primary intestine-moistening component); polysaccharides; amino acids.

• Expectorant, antitussive, and anti-asthmatic: inhibits airway inflammation; thins mucus viscosity; relaxes bronchial smooth muscle; effectively relieves cough, copious phlegm, and dyspnoea; improves respiratory conditions
• Cardiovascular protection: dilates coronary arteries; improves myocardial blood supply; reduces vascular resistance; inhibits platelet aggregation; adjunctive in chest stuffiness, chest bi-obstruction, and myocardial ischaemia
• Gentle laxative: oil-rich seeds lubricate intestinal wall; promote intestinal peristalsis; gentle improvement of intestinal-Dryness constipation without stimulant laxative effect
• Anti-inflammatory and sore-resolving: inhibits inflammatory responses; reduces skin carbuncle-sore swellings, breast inflammation; promotes inflammatory exudate resolution
• Hypoglycaemic and antioxidant: improves metabolic function; scavenges free radicals; adjunctive in Dryness-Heat wasting-thirst; enhances antioxidant capacity

VIII. Dosage and Safety

Suitable populations: Lung-Heat with yellow thick sticky phlegm, copious Phlegm difficult to expectorate; chest stuffiness and oppression, chest-bi Qi-stagnation binding, chest-before-the-sternum pain; Lung-Dryness dry cough, fluid-Yin depletion dry stool, habitual intestinal-Dryness constipation; breast carbuncle, Lung carbuncle, sore-Heat-toxin binding; Lung-Stomach Dryness-Heat, vexing thirst and wasting-thirst.

Dosage: decoction: Quan Gua Lou 9–15g; Gua Lou Pi 6–10g; Gua Lou Ren 10–15g (crushed before decocting). Processing selection: moisten-Dryness stop-cough — honey-fried Gua Lou; clear Heat resolve Phlegm — raw Gua Lou. Do not use in excessive doses or long-term to avoid Cold-damaging Spleen and slipping intestine excess.

Contraindications:

• Spleen-Stomach deficiency-Cold, loose stool and diarrhoea: Gua Lou’s cold moist nature worsens Spleen-Stomach deficiency-Cold; causes diarrhoea, abdominal bloating, and abdominal cold-pain; contraindicated
• Cold-Damp Phlegm and Damp-Phlegm cough-dyspnoea: Cold-type Phlegm-Damp cough using the cold-cooling Gua Lou will worsen Phlegm-Damp congealing, aggravating cough-dyspnoea; contraindicated
• Low blood pressure and bleeding tendency: Gua Lou’s vasodilating and antiplatelet actions may worsen dizziness and bleeding; use with caution
• Pregnancy, constitutional chronic diarrhoea: cold-moist slipping nature; risks Spleen-Yang damage in constitutionally weak patients with chronic diarrhoea; use with caution
• Incompatibilities (Shi Ba Fan): CRITICAL — Gua Lou conflicts with Wu Tou (Aconite root, including Chuan Wu, Cao Wu, Fu Zi): ABSOLUTELY PROHIBITED. This is one of the most clinically important Eighteen Incompatibilities prohibitions. Also: aversion to Gan Jiang and Niu Xi — avoid combining