Tea Tree

The tea tree grows in Australia and Asia. This tall evergreen tree has a white, spongy bark. The oil from the leaves is used medicinally.

Australian Aborigines used the leaves to treat cuts and skin infections. They would crush the leaves and apply them to the affected area. Captain James Cook and his crew named the tree "tea tree," using its leaves as a substitute for tea as well as to flavor beer. Australian soldiers participating in World War I were given tea tree oil as a disinfectant, leading to a high demand for its production.

The oil contains numerous chemicals known as terpenoids. Australian standards were established for the amount of one particular compound, terpinen-4-ol, which must make up at least 30% and preferably 40–50% of the oil for it to be medically useful. Another compound, cineole, should make up less than 15% and preferably 2.5% of the oil. The oil kills fungus and bacteria, including those resistant to some antibiotics.^{1, 2} For common acne, a double-blind trial compared the topical use of 5% tea tree oil to 5% benzoyl peroxide.³ Although the tea tree oil was slower and less potent in its action, it had far fewer side effects and was thus considered more effective overall.

A double-blind trial found that a 10% tea tree oil cream was as effective as anti-fungal medicine at improving symptoms associated with athlete's foot, though it was not more effective than a placebo for eliminating the fungal infection.⁴ A double-blind trial found 100% tea tree oil applied topically was as effective as the anti-fungal medicine clotrimazole (Lotrimin®, Mycelex®) for people with fungus affecting the toe nails, a condition known as onychomycosis.⁵ In another double-blind trial with toenail fungus sufferers, a combination of 5% tea tree oil and 2% butenafine (Mentax®), a synthetic anti-fungal drug, in a cream proved more effective than an unspecified concentration of tea tree oil in cream alone.⁶ The results are not entirely surprising, as the tea tree product alone was probably not at a sufficiently high enough concentration to be effective.

A preliminary trial found that rinsing the mouth with 1 tablespoon (15 ml) tea tree oil solution four times daily effectively treated thrush (oral yeast infections) in AIDS patients.⁷ Solutions containing no more than 5% should be used orally and should never be swallowed.

A concern for hospital staff and patients is the spread of the bacteria Staphylococcus aureus—sometimes referred to as a "staph infection." One small clinical trial found that use of a 4% tea tree oil nasal ointment as well as a 5% tea tree oil body wash was slightly more effective than standard drugs used to prevent the spread of the bacteria.⁸

Oil at a strength of 70–100% should be applied moderately at least twice per day to the affected areas of skin or nail.⁹ For topical treatment of acne, the oil is used at a dilution of 5–15%. Concentrations as strong as 40% may be used—with extreme caution and qualified advice—as vaginal douches. For thrush in immune-compromised adults, tea tree oil diluted to 5% or less is used in the amount of 1 tablespoon (15 ml) four times daily (as a mouth rinse). Tea tree oil should never be swallowed.

While tea tree oil can be applied to minor cuts and scrapes, use caution for more extensive areas of broken skin or areas affected by rashes not due to fungus. The oil may burn if it gets into the eyes, nose, mouth, or other tender areas. Some people have allergic reactions, including rashes and itching, when applying tea tree oil.¹⁰ For this reason, only a small amount should be applied when first using it.

In case reports, three young boys developed breast enlargement (gynecomastia) after repeated topical application of products that contained lavender oil and tea tree oil. The problem resolved after they stopped using the oils. While a cause–effect relationship was not conclusively proven, it was suggested by the fact that these oils have been found to have estrogen-like effects in test tube studies.¹¹ Tea tree oil should never be swallowed, as it may cause nerve damage and other problems.