Tea tree oil (Melaleuca alternifolia [Maiden & Betche] Cheel)

Tea tree oil is obtained by steam distillation of the leaves of Melaleuca alternifolia. Tea tree oil is purported to have antiseptic properties and has been used traditionally to prevent and treat infections. While numerous laboratory studies have demonstrated antimicrobial properties of tea tree oil (likely due to the compound terpinen-4-ol), only a small number of high-quality trials have been published. Human studies have focused on the use of topical tea tree oil for fungal infections (including fungal infections of the nails and athlete's foot), acne, and vaginal infections. However, there is a lack of definitive available evidence for the use of tea tree oil in any of these conditions, and further study is warranted.

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Medicinal use

Tea tree oil has been recognized as a potent antiseptic in Australia anecdotally for much longer than there has been scientific evidence. However, recent studies support a role for tea tree oil in skin care and treatment of various ailments.

Tea tree oil has activity against staphylococcus aureus including MRSA, and when used at 10% concentration is comparable with Mupirocin for application to the skin but has never been shown to cause resistance. However, this can occur at lower percentages. It is less successful for application in the nose.

Tea tree oil is a known antifungal agent, effective in vitro against multiple dermatophytes found on the skin. In vivo, shampoo with 5% tea tree oil has been shown to be an effective treatment for dandruff due to its ability to treat Malassezia furfur, the most common cause of the condition.

Effectiveness of topical tea tree oil preparations for Candidiasis is supported by its ability to kill Candida in vitro.

In the treatment of moderate acne, topical application of 5% tea tree oil has shown an effect comparable to 5% benzoyl peroxide, albeit with slower onset of action. In another study in 2007 5% strength gel was compared against a placebo, with statistically significant results.

There is some very limited research that has shown that tea tree oil may have topical anti-viral activity, especially with the Herpes virus (cold sores, chicken pox and shingles blisters, etc).

There is clinical evidence that topical dermatological preparations containing tea tree oil may be more effective than conventional antibiotics in preventing transmittal of CA-MRSA.

One study has shown a 5% tea tree oil solution to be more effective than commercial medications against the scabies mite in an in vitro situation.

Diluted solutions of tea tree oil are often used as a remedy to treat bacterial and fungal infection in aquarium fish. Common brand names are Melafix and Bettafix. Melafix is a stronger dilution and Bettafix is a lighter dilution that makes it harder to overdose smaller (especially Betta) fish. It is most commonly used to promote fin and tissue regrowth but is also effective in treating other conditions such as fin rot or velvet. The remedy is used mostly on Betta fish but can also be used with other aquarium fish.