Before red light gained a reputation in the beauty industry, dermatologists used it for early-stage treatment of precancerous and early, thin skin cancers, said Nour Kibbi, MD, clinical assistant professor of dermatology. Red light applied at a specific wavelength in conjunction with a topical drug kills skin cells, a type of treatment called photodynamic therapy. (Red light, alone, does not destroy skin cancer.) When applied to damaged or diseased skin cells, such as cancer cells, those cells die off and allow for the growth of new skin.