Tea tree oil
Tea tree oil, or melaleuca oil, is a pale yellow colour to nearly colorless and clear essential oil with a fresh camphoraceous odor. It is taken from the leaves of the Melaleuca alternifolia, which is native to the northeast coast of New South Wales, Australia. Tea tree oil should not be confused with tea oil, the sweet seasoning and cooking oil from pressed seeds of the tea plant Camellia sinensis (beverage tea), or the tea oil plant Camellia oleifera.
Tea tree oil has been scientifically investigated only recently. Some sources suggest beneficial medical properties when applied topically, including antiviral, antibacterial, antifungal, and antiseptic qualities. It also has beneficial cosmetic properties.
Tea tree oil is active against Staphylococcus aureus, including MRSA. Tea tree oil is less successful for application in the nose. Also, there is clinical evidence that topical dermatological preparations containing tea tree oil may be more effective than conventional antibiotics in preventing transmission of CA-MRSA.
Recent studies support a role for the topical application of tea tree oil in skin care and for the treatment of various diseases and conditions. Tea tree oil appears to be effective against bacteria, viruses, fungal infections, mites such as scabies, and lice such as head lice. A 2008 study of in vitro toxicity showed a tea tree oil preparation was more effective against head lice than permethrin, a popular pharmaceutical remedy.
In the treatment of moderate common acne, topical application of 5% tea tree oil has shown an effect comparable to 5% benzoyl peroxide. Albeit with slower onset of action, patients who use tea tree oil experience fewer side effects than those that use benzoyl peroxide treatments. 
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.
One clinical study found that 100% tea tree oil administered topically, combined with debridement, was comparable to clotrimazole in effectiveness against onychomycosis, the most frequent cause of nail disease.
The effectiveness of topical tea tree oil preparations for the treatment of the yeast infection Candidiasis is supported by its ability to kill Candida in vitro.
There is some very limited research that has shown that tea tree oil may have topical antiviral activity, especially against the herpes virus (cold sores), chicken pox, 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.