Photodynamic therapy (PDT) is a treatment that uses a drug, called a photosensitizer, and a particular kind of light. The photosensitizer, 5-aminolevulinic acid (5-ALA), is applied to the skin and allowed to incubate for duration of 1-3 hours. Once the skin has properly absorbed the agent, the patient is exposed to a therapeutic light source of a particular wavelength with a blue hue. For this reason, the treatment is also called Blue Light therapy.
When the area to be treated is exposed to the light, precancerous and cancerous cells are destroyed. PDT is used for many different dermatologic conditions including actinic keratoses (precancers), skin cancers, photodamage, acne, hidradenitis suppurativa and Bowen's disease. The light kills any precancerous or cancerous cell that has absorbed the 5-ALA. It also increases cell turnover and stimulates collagen in an effort to treat sun damage. Downtime associated with the procedure is minimal and referred to as the "PDT effect." It includes redness, peeling and scaliness and typically takes less than one week. Patients who have severe reactions often have excellent results.