Transfer of energy from photo-excited dye molecules to oxygen molecules results in the production of a highly reactive type of oxygen that damages tumor components. Lasers equipped with fiber optics allow non-invasive treatment of tumors in body cavities such as the esophagus, lungs and bladder. The main side effect of current photosensitizers is a residual skin photosensitivity. Photodermatology Photodermatology includes harmful and therapeutic interactions of light with skin. Interaction of UV light with the skin causes a complicated cascade of events that involve cellular damage and repair, pigmentation changes, vascular and immune effects.
Research is ongoing to determine the molecular nature of UV-induced sunburn and skin cancer.
Ultraviolet light is used therapeutically in PUVA, topical administration of psoralen followed by exposure to UVA light in the range of 320 to 380 nm. PUVA is an effective treatment for psoriasis, eczema and vitiligo. Absorption of green light by hemoglobin is the basis for treatment of hypervascular birthmarks and varicose veins with argon, KTP or dye lasers. Visible and near-infrared lasers are also used for the removal of hair, tattoo's and pigmented lesions. This group of diseases includes both phototoxic and photoallergic effects.