Transforms Dampness and harmonises the Middle Jiao — principal aromatic Dampness-transforming herb; nausea, vomiting, epigastric fullness, abdominal distension, and diarrhea from Damp obstructing Spleen-Stomach
Releases exterior and dispels Summer-Heat-Damp — summer febrile illness with fever, chills, nausea, heavy limbs, and diarrhea from Wind-Cold attacking surface while interior Dampness is present
Stops vomiting — one of the premier anti-emetic herbs in TCM; effective for vomiting from multiple causes including morning sickness, motion sickness, and post-operative nausea
Secondary Actions
Aromatic digestive — stimulates gastric secretion, promotes intestinal motility; used for poor appetite, bloating, and nausea in Damp-Cold Spleen patterns
Antifungal topical use — strong essential oil used for tinea pedis, athlete's foot, and oral candidiasis in folk practice
Classic Formulas
Huo Xiang Zheng Qi San (藿香正气散) — one of the most widely prescribed formulas in Chinese medicine; Huo Xiang combined with Bai Zhi, Zi Su, Hou Po, Ban Xia, Bai Zhu, Fu Ling, Chen Pi, Jie Geng, Da Fu Pi, and Zhi Gan Cao; for Exterior Wind-Cold with Interior Damp; summer gastroenteritis, food poisoning, motion sickness, and diarrhoea from summer cold; sold as Huo Xiang Zheng Qi Wan (pills) and liquid — one of the most commercially available OTC Chinese herbal medicines
Huo Xiang Huang Lian Tang (藿香黄连汤) — combined with Huang Lian (黄连) for Damp-Heat nausea and vomiting; Stomach rebelliousness with Damp-Heat signs
Classical References
Jing Yue Quan Shu (景岳全书, Zhang Jingyue, 1624): 'Huo Xiang (aromatic herb) is the commander of all aromatic herbs that transform Dampness — it awakens the Spleen, harmonises the Stomach, stops vomiting, and resolves summer-heat; combined with other aromatic Damp-transforming herbs it treats all exterior-interior combined Damp disorders'
SPECIES NOTE: Two distinct plants are called Huo Xiang in Chinese medicine: (1) Agastache rugosa (Fischer & Meyer) Kuntze (土藿香, Tu Huo Xiang — 'local Huo Xiang'; Lamiaceae; this herb #86, Herba Agastaches), used primarily in northern China; (2) Pogostemon cablin (Blanco) Benth. (广藿香, Guang Huo Xiang — 'Guangdong Huo Xiang'; also Lamiaceae; the official Chinese Pharmacopoeia 2020 species for Huo Xiang Zheng Qi formulas). Agastache rugosa is widely used as a substitute but has a different essential oil composition (methyl chavicol-dominant vs. patchouli-oil-dominant)
Modern Research
Active Compounds
Methyl chavicol (estragole; ~70–80% of essential oil; antimicrobial, antispasmodic, anti-inflammatory)
Anti-emetic and gastrointestinal: essential oil from Agastache rugosa relaxes intestinal smooth muscle via Ca2+-channel antagonism and 5-HT3 receptor modulation; antiemetic activity confirmed in cisplatin-induced emesis models and gastric emptying studies — validates the anti-vomiting and Stomach-harmonising TCM application and provides a mechanistic basis for the use in Huo Xiang Zheng Qi San
Antimicrobial and antifungal: methyl chavicol and anisaldehyde from A. rugosa essential oil exhibit broad-spectrum antimicrobial activity against Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Candida albicans in MIC assays; anti-biofilm activity against oral pathogens also demonstrated — consistent with the summer diarrhea, gastroenteritis, and topical antifungal applications
Anti-inflammatory: rosmarinic acid and apigenin from A. rugosa inhibit NF-κB, COX-2, and TNF-α/IL-6 in LPS-activated macrophage models; in vivo anti-inflammatory efficacy confirmed in carrageenan paw edema assay — supports the Summer-Heat-Damp releasing and fever-associated inflammation applications
Safety & Interactions
Contraindications
Yin Deficiency with Heat or interior Heat patterns — pungent-warm aromatic nature will aggravate deficiency Heat, dry fluids, and worsen thirst
Excess Heat patterns without Dampness — aromatic warming herbs contraindicated with pure Heat presentations
Cautions
Standard dose: 6–12 g dried herb; add near end of decocting (last 10–15 minutes) to preserve volatile essential oils — prolonged boiling destroys therapeutic aromatics
Methyl chavicol (estragole) in the essential oil is classified as a potential genotoxin and carcinogen in concentrated form by EFSA and HMPC; at standard therapeutic decoction doses the exposure is negligible and not clinically concerning; avoid prolonged use of high-concentration essential oil preparations
Agastache rugosa vs. Pogostemon cablin substitution: the two plants have different essential oil compositions; clinical substitution in Huo Xiang Zheng Qi San should be noted as non-pharmacopoeial
Pregnancy: aromatic/pungent herbs traditionally used cautiously in pregnancy; short-term use at standard doses for morning sickness generally considered acceptable in TCM practice