Photodynamic therapy (PDT) is used to treat precancerous skin lesions (actinic keratoses), superficial basal cell carcinomas and other skin changes. When applied to large areas, it also has a skin-rejuvenating effect.
In PDT, the diseased areas of skin are treated with a cream (photosensitizer such as 5-aminolevulinic acid or its methylated form, Metvix). This cream is left to work for about 2–3 hours. Then the skin is exposed to a special type of visible light for approximately 10 minutes. As the light is absorbed, the diseased tissue is destroyed in a targeted manner by a special type of oxygen called singlet oxygen.