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 illness 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.