Tea tree oil a kind of green tea extract 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 as well as grape seed extract and verbascoside are 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 their 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.)

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.