Research suggests caffeine in tea (coffee too) may help to protect your skin against skin cancer. Caffeine basically kills precancerous and ultraviolet-damaged skin cells by blocking a protein that they need to divide, explains Paul Nghiem, M.D., Ph.D., associate professor of dermatology at the University of Washington Medical School. In a study where mice were exposed to harmful sunburn-causing ultraviolet B rays caffeine inhibited the formation of skin tumors.