The Next Miracle Tree: Tea Tree and Its Relatives

The Scientific Record

In 1925, Arthur Penfold, a chemist at the Museum of Technology and Applied Sciences in Sydney, Australia, published research results that showed the antiseptic activity of Melaleuca alternifolia oil to be up to thirteen times that of carbolic acid, then a well-known germicide. In 1930, an article in The Medicinal Journal of Australia revealed that the oil, when applied to carbuncles and other pus-filled infections, dissolved pus and had a powerful antibacterial effect without damaging surrounding tissues as carbolic acid did.

Those two studies confirming the antibacterial properties of tea tree oil were the sole scientific basis of claims for its effectiveness until 1990, when dermatologists at Royal Prince Alfred Hospital in Camperdown, New South Wales, published in The Medicinal Journal of Australia the results of a clinical study of tea tree oil’s effect on facial acne. The single-blind study, involving 124 persons with mild to moderate acne, showed that a 5 percent tea tree oil gel was as effective against acne as a 5 percent benzoyl peroxide lotion, a common and effective acne treatment. In addition, the tea tree oil gel caused significantly less skin scaling, dryness, itching, and irritation than the benzoyl peroxide preparation. In light of these results, it seems odd that the tea tree oil-based acne treatment most readily available in this country is openly promoted as containing large quantities of benzoyl peroxide.

Another scientific study of tea tree oil was conducted in 1992, also by dermatologists at Royal Prince Alfred Hospital, on 104 persons with athlete’s foot (caused by the fungus Tinea pedis). In this randomized double-blind study, the results of which were published in the Australasian Journal of Dermatology, patients were treated with creams containing either 10 percent tea tree oil, 1 percent tolnaftate (a popular and effective athlete’s foot treatment), or no medication. Symptoms of scaling, inflammation, itching, and burning were monitored throughout the study; at the conclusion of treatment, patients were tested for the presence of T. pedis. Although the tea tree oil cream was as effective as tolnaftate in relieving athlete’s foot symptoms, it did not perform significantly better than the placebo (unmedicated cream) in eliminating the fungus.

The toxicity of tea tree oil has yet to be examined scientifically. Australians have drunk the leaf tea regularly for centuries with no reported ill effects, but the chemical composition of a water extract undoubtedly differs greatly from that of the distilled essence. Toxic thresholds have not been determined for internal use of either the tea or the oil. Like many other herbal essential oils, pure tea tree oil dissolves certain plastics, irritates the eyes and mucous membranes, and often causes irritation when applied undiluted to the skin.

In Australia, M. alternifolia oil that is rich in terpinen-4-ol is generally considered antibacterial and germicidal and is used in treatments for acne, infected wounds, and many other kinds of skin infections and lesions. Other conditions for which its use has been commercially promoted include arthritis, bruises, burns (including sunburn), cystitis, all kinds of dermatitis, most fungal and herpes infections, insect bites, muscle aches and pain, varicose veins, respiratory tract infections, vaginal yeast infections, and warts.

Topical applications clearly provide temporary relief of symptoms in many of these conditions, but further research is needed to confirm most therapeutic claims. The United States Food and Drug Administration allows tea tree oil only as a fragrance component and, in cosmetic preparations, for its antibacterial properties; to date, no other therapeutic claims have been approved.