Tea tree oil, also known as melaleuca oil, is an essential oil that comes from steaming the leaves of the Australian tea tree.

When used topically, tea tree oil is believed to be antibacterial. Tea tree oil is commonly used to treat acne, athlete's foot, lice, nail fungus and insect bites.

Tea tree oil is available as an oil and in many over-the-counter skin products, including soaps and lotions. However, tea tree oil should not be taken orally. If swallowed, it can cause serious symptoms.

Research on tea tree oil use for specific conditions shows:

• Acne. Research suggests that a treatment gel containing tea tree oil might be effective at relieving acne.
• Dandruff. A tea tree oil shampoo used for four weeks has been shown to be effective at treating dandruff.
• Athlete's foot. A tea tree oil cream, applied twice daily for one month, has been shown to be effective in relieving symptoms of athlete's foot.
• Lice. When used in combination with lavender oil, tea tree oil has been shown to be effective at treating lice eggs.
• Nail fungus. Research hasn't shown tea tree oil used in its pure form or in combination with other antifungal therapies to be effective in treating toenail fungus.

Results might vary because there are no standardized methods for harvesting tea tree oil or creating products containing the oil.

Most people can use tea tree oil topically with no problems. However, tea tree oil can cause:

• Skin irritation
• Allergic skin rash (dermatitis)
• Itching
• Stinging
• Burning
• Scaling
• Redness
• Dryness

Don't use tea tree oil if you have eczema.

Tea tree oil is toxic when swallowed. Serious side effects can occur, including:

• Confusion
• A lack of muscle control or coordination of voluntary movements (ataxia)
• Decreasing levels of consciousness

One study suggests that repeated exposure to lavender oil and tea tree oil might have led to the swelling of the breast tissue (gynecomastia) in young boys.

Although tea tree oil is often used in combination with other drugs when treating bacterial or fungal skin conditions, there's currently no evidence showing drug interactions.