Tea tree oil comes from the leaves of a native Australian plant. Originally, the leaves were used as a substitute for tea, and that's how the tree got its name. The aborigines saw the benefits of tea tree leaves and used them for a number of skin irritations. They would crush the leaves and put them directly on the infected area and found it quite effective due to it's antiseptic, antibacterial and anti-fungal properties. The oil from the leaves contains terpenoids, which gives it the antiseptic and anti-fungal characteristics. Psoriasis patients have found some relief with tea tree oil in its pure form, not as an ingredient in another product.