Blue light therapy, a form of photodynamic therapy, treats skin with special photosensitive chemicals before exposing it to a blue light, which reacts with the chemicals to generate reactive oxygen radicals that destroy potentially precancerous lesions called actinic keratoses, according to the American Cancer Society. Aminolevulinic acid, the photosensitizing chemical agent applied directly to the lesions, is left on the skin for 14 to 18 hours before blue light therapy.
Actinic keratoses are scaly lesions ranging in size from a pinhead to 1 inch, according to the University of Iowa Hospitals & Clinics. The bumps show up mostly in sun-exposed areas of the face, head, lips, ears and back of the hands and forearms. When left untreated, about 10 percent of these bumps may eventually evolve into a kind of skin cancer called squamous cell carcinoma.
Patients with actinic keratoses historically have been treated mainly with cryotherapy, which uses liquid nitrogen for freezing the skin, according to University of Iowa Hospitals & Clinics. However, cryotherapy can sting, and it is impractical for treating large areas of skin, Another treatment, topical chemotherapy, is capable of treating larger areas but typically results in inflammation. Blue light therapy increasingly is available as a treatment option.