To relieve dandruff, wash your hair and scalp daily with shampoo that contains tea tree oil, and continue the treatment for four weeks. Pure tea tree oil may be purchased from many health food stores and added to your favorite shampoo. The recommended concentration is a 5 percent solution of oil in shampoo, or about one tsp. of oil in a 100 ml bottle. Alternatively, some products are available in pharmacies with tea tree oil already added.