Researchers have found that tea tree oil may be a fast, inexpensive, and effective treatment for some forms of skin cancer. In a recent study, investigators found that the natural remedy--which is sometimes used on insect bites and acne--shrunk non-melanoma skin cancers in mice after just one day and eradicated the cancers within three days. The scientists say tea tree oil, which is derived from a plant in New South Wales in Australia, may work by activating the body's immune response.