# Tea tree oil (Melaleuca alternifolia)

*Australian tea tree; melaleuca oil, the name approved in Australia, and the older ‘ti tree oil’; *Melaleuca alternifolia* (Maiden and Betch) Cheel, with *M. linariifolia* Smith and *M. dissitiflora* F. Mueller; in pharmacy *Melaleucae aetheroleum**

**Known today as.** The essential oil steam-distilled from the leaves and end branchlets of *Melaleuca alternifolia*, a tree of the family Myrtaceae, which the European Medicines Agency’s assessment report says was named tea tree “because the leaves were used to prepare an aromatic tea.” Before it was cultivated its natural range was limited to the country around the Clarence and Richmond Rivers on the north-eastern coast of New South Wales; the oil now comes mainly from large plantations in New South Wales and Queensland. It is a clear, colourless or pale yellow liquid with “a distinct pleasant odour like turpentine,” about 2 per cent of the leaf.

Kind: Plant

> **Caution.** Not to be swallowed or inhaled, nor used in the eyes or ears, nor under twelve, nor by anyone allergic to it or to colophony. Stop if a rash develops. Smarting, itching, burning, redness, and contact dermatitis have been reported, and rarely burn-like reactions of the skin; the 2023 review found side effects minor except where the oil was applied at 25 per cent or more. Accidental ingestion can cause depression of the central nervous system and muscle weakness, and in children, the European agency warns, swallowing tea tree oil “is a medical emergency requiring immediate hospital treatment and respiratory support.”

## What was it used for?

An antiseptic for the skin and mouth. The assessment report, following Carson and Riley, records its use by “Australian Bundjabung Aborigines” for several millennia for bruises, insect bites, and skin infections, and that it was rediscovered in the 1920s as a topical antiseptic “with more effective activity than phenol,” becoming a standard antiseptic for surgery, especially dental surgery. The British Pharmaceutical Codex of 1949 gave it as germicidal, applied to furunculosis, tinea, paronychia, impetigo, thrush, and stomatitis and inhaled in coryza; a 2023 review adds that First Nations Australians used the leaves for wounds, burns, and insect bites.

## What does modern science say?

The European Medicines Agency’s herbal committee accepts the oil, for use on the skin and in the mouth only, as a traditional herbal medicine, “exclusively based upon long-standing use,” for small superficial wounds and insect bites, small boils and mild acne, the itching and irritation of mild athlete’s foot, and minor inflammation of the lining of the mouth (monograph of 2015). Its assessment report finds the oil made largely of cyclic monoterpenes, terpinen-4-ol chief among them at about 42 per cent in one analysis; the European Pharmacopoeia requires at least 30 per cent of terpinen-4-ol and at most 15 per cent of 1,8-cineole, which is probably an unwanted allergen. A 2023 review of forty-six randomised trials judged their quality poor to modest: mouthwashes may limit dental plaque, gels may aid the treatment of periodontitis, and topical regimens were about as effective as standard treatment in clearing MRSA from the body, but more evidence was needed for acne. A 2026 meta-analysis of seven acne studies found a modest reduction in severity. A Cochrane review of 2020 found the effect of 5 to 50 per cent tea tree oil on Demodex mites of the eyelids uncertain.

## Pharmacognosy and toxicology

- **terpinen-4-ol**: chief of the cyclic monoterpenes, about 42 per cent in one analysis; at least 30 per cent required
- **1,8-cineole**: at most 15 per cent; probably an unwanted allergen

**Mechanism.** Not established in the sources read for this entry.

**Standing.** European Union herbal monograph (2015): traditional use on the skin and in the mouth, “exclusively based upon long-standing use,” for minor wounds, insect bites, mild acne, athlete’s foot, and mouth inflammation. Not to be swallowed.

## What lore surrounds it?

In veterinary practice, the 1949 Codex adds, it was used for mange and eczema and for sores and skin diseases of parasitic origin. The name ti tree, the assessment report notes, belongs properly to the Maori and Samoan name for plants of another genus, *Cordyline*.

## Sources

- European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Melaleucae aetheroleum (Tea-tree oil)*. EMA/HMPC/320930/2012, 24 November 2015.
- European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Melaleucae aetheroleum*. EMA/HMPC/320932/2012, 24 November 2014.
- Kairey L, et al. (2023). Efficacy and safety of <i>Melaleuca alternifolia</i> (tea tree) oil for human health-A systematic review of randomized controlled trials. *Frontiers in pharmacology*. PMID 37033604.
- Ye Y, et al. (2026). Efficacy and Safety of Melaleuca alternifolia (Tea Tree) Oil for Acne-A Systematic Review and Meta-Analysis. *Phytotherapy research : PTR*. PMID 42098589.
- Savla K, et al. (2020). Tea tree oil for Demodex blepharitis. *The Cochrane database of systematic reviews*. PMID 32589270.
- European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Melaleucae aetheroleum (Tea-tree oil)*. EMA/HMPC/320930/2012, 24 November 2015.
- European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Melaleucae aetheroleum*. EMA/HMPC/320932/2012, 24 November 2014.
- Kairey L, et al. (2023). Efficacy and safety of <i>Melaleuca alternifolia</i> (tea tree) oil for human health-A systematic review of randomized controlled trials. *Frontiers in pharmacology*. PMID 37033604.
- Savla K, et al. (2020). Tea tree oil for Demodex blepharitis. *The Cochrane database of systematic reviews*. PMID 32589270.

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*Tea tree oil.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-16. The Thinking Press. https://thethinkingpress.org/materia-medica/tea-tree-oil

Historical description, not medical advice.