Zhang Nao
StarCinnamomum camphora (L.) Presl.
☯ TCM Properties
Clears Heat and Resolves Phlegm from the Orifices; Moves Qi and Resolves Stagnation; Kills Parasites and Stops Itching; Reduces Swelling and Alleviates Pain; Warms the Middle Burner and Stops Pain; Drains Dampness
Traditional Chinese Uses
Zhang Nao (camphor) is a warm, pungent aromatic substance used in Chinese medicine primarily as an external remedy to open the orifices, relieve pain, kill parasites, and stop itching. It is applied topically for scabies, ringworm, skin sores, joint pain, and traumatic injuries. Its penetrating, aromatic nature allows it to disperse cold and obstruction from the channels and sinew when used externally. Internal use is limited, as camphor is toxic if ingested in significant amounts, and its primary role is firmly in external applications.
Western Herbalism Properties
Botanical Description
Cinnamomum camphora, the camphor tree, is a large evergreen tree in the family Lauraceae, native to East Asia, particularly southern China, Taiwan, southern Japan, and Vietnam, and widely planted in subtropical regions worldwide. Mature specimens commonly reach 20-30 meters in height with broad, dome-shaped crowns and stout, deeply furrowed grayish-brown trunks. The alternate, ovate to elliptic leaves are leathery and glossy, with three prominent veins from the base, and emit a strong camphor scent when crushed. Small, six-tepalled, pale yellow-green flowers are borne in axillary panicles in spring, developing into round, dark-purple to black drupes about 1 cm across. All tissues, especially the wood and leaves, contain volatile oil rich in camphor crystals that are distilled and harvested commercially.
Active Constituents
(+)-Camphor
Bicyclic monoterpene ketoneConcentration: Principal component; up to ~95% of the crystalline sublimate and of camphor-chemotype essential oil
The characteristic active principle. Acts as a rubefacient and counterirritant on skin and mucosa, producing local warmth followed by a cooling, analgesic and antipruritic sensation via TRPV1/TRPV3 and TRPM8 channel modulation. It is aromatic, antiseptic and insecticidal, and at toxic systemic doses it is a CNS stimulant that lowers the seizure threshold.
Safrole
Phenylpropanoid (methylenedioxy)Concentration: Dominant in the safrole ("brown camphor") chemotype, trace to minor in the camphor chemotype
A fragrant phenylpropanoid contributing to antimicrobial and insecticidal activity. It is hepatotoxic and a recognized genotoxic carcinogen, and its abundance varies markedly between chemotypes, which is a key safety consideration for the raw material.
1,8-Cineole (eucalyptol)
Monoterpene ether (oxide)Concentration: Major in the cineole chemotype; minor in others
Contributes expectorant, mucolytic, anti-inflammatory and antimicrobial properties, and reinforces the penetrating, decongestant aroma used in topical liniments.
Linalool
Acyclic monoterpene alcoholConcentration: Dominant in the linalool chemotype ("ho wood/ho leaf" oil); minor elsewhere
A floral monoterpene alcohol with sedative, anxiolytic and antimicrobial activity; contributes to the aroma and to mild anti-inflammatory effects.
Camphene
Bicyclic monoterpene hydrocarbonConcentration: Minor constituent of the volatile oil
A lipophilic terpene with antioxidant and antimicrobial activity; contributes to skin penetration of the topical preparation.
alpha-Pinene
Bicyclic monoterpene hydrocarbonConcentration: Minor constituent of the volatile oil
Volatile terpene with anti-inflammatory, bronchodilatory and antimicrobial activity; enhances aromatic and counterirritant qualities.
Limonene
Monocyclic monoterpene hydrocarbonConcentration: Minor constituent of the volatile oil
Citrus-scented terpene with antioxidant, anti-inflammatory and mild antimicrobial activity; aids solubilization and skin penetration.
Borneol
Bicyclic monoterpene alcoholConcentration: Minor constituent (biosynthetic relative of camphor)
Aromatic "orifice-opening" alcohol that promotes penetration of co-administered agents across skin and mucosa; mild analgesic and antimicrobial.
⚠ Drug Interactions
Anticonvulsants / antiepileptic drugs (e.g., phenobarbital, valproate)
Absorbed camphor is a CNS stimulant that lowers the seizure threshold; even topical or inhaled exposure has produced convulsions, particularly in children. This can counteract anticonvulsant therapy and precipitate breakthrough seizures in predisposed patients.
Clinical note: Avoid in patients with epilepsy or seizure history; keep away from children. Use only externally on intact skin and never on broken skin or the face of infants.
Hepatotoxic drugs / agents metabolized by hepatic conjugation (e.g., acetaminophen, isoniazid)
Camphor is metabolized in the liver by cytochrome P450 oxidation and glucuronide conjugation. Safrole, a variable co-constituent, is hepatotoxic and genotoxic. Concurrent hepatotoxic drugs may compound the load on hepatic detoxification pathways with excessive or prolonged use.
Clinical note: Limit dose and duration; avoid in hepatic impairment. Systemic (oral) use is discouraged given the narrow margin of safety.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| powder | 0.3-1g | Daily | — | — | — |
Preparation Methods
Topical application (powder, medicated oil, liniment or plaster)
Parts: Refined crystalline camphor (sublimate of wood/leaf distillate)
The principal traditional and modern use. Finely powdered camphor is dissolved in oil or alcohol, or incorporated into ointments and plasters, and applied externally to affected skin for itching, ringworm, scabies, sores and localized pain and swelling. It is a warming counterirritant. Do not apply to broken skin, mucous membranes, or the face of infants and young children.
Small-dose internal use in pills/powders (specialist use only)
Parts: Refined crystalline camphor
Historically incorporated in tiny amounts (roughly 0.1-0.2 g) into pills or powders to open the orifices and revive consciousness or warm the middle and stop pain. Camphor is never decocted because it sublimes and volatilizes on heating. Because of its narrow toxic margin this internal route is now rarely used and requires expert supervision; it is contraindicated in pregnancy and in the deficient or heat-pattern patient.
Clinical Studies
A cluster of children with seizures caused by camphor poisoning
Report of three young children (15-36 months) who developed seizures after ingestion or repeated dermal application of camphor-containing products, all requiring pharmacologic intervention. The series underscores the low toxic threshold of camphor and the neurotoxic (pro-convulsant) hazard that governs its safe, external-only, low-dose use.
Historical Texts
Ben Cao Pin Hui Jing Yao (Collected Essentials of Materia Medica)
Ming dynasty, 1505Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1596References
- Chen W, Vermaak I, Viljoen A. Camphor - A Fumigant during the Black Death and a Coveted Fragrant Wood in Ancient Egypt and Babylon - A Review . Molecules (2013) [DOI]
- Khine H, Weiss D, Graber N, Hoffman RS, Esteban-Cruciani N, Avner JR. A cluster of children with seizures caused by camphor poisoning . Pediatrics (2009) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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