Photodynamic Therapy (PDT) is used to treat pre-cancerous lesions, also known as Actinic Keratosis. It is important to treat these lesions as some of them may progress to squamous cell carcinoma (SCC), the second most common form of skin cancer. PDT therapy involves three steps. The first step is “the application” of Levulan (Aminolevulinic Acid 20%) to the skin followed by “incubation”, where the medication sits on the skin for 1-2 hrs. The last step involves the blue light being applied to the area to “activate” the medication. This therapy has been FDA approved. Possible side effects of this treatment include discomfort, burning, swelling, blistering, redness and possible skin peeling, especially in any areas of sun damaged skin and pre-cancerous lesions of the skin. The peeling may last approximately one week, especially if there is an exuberant response to the treatment. This therapy is not appropriate if you have certain conditions, such as being pregnant or having a photosensitivity disorder (such as lupus or porphyria), or if you are taking certain medications (or other vitamins or herbs) that may contain photosensitizing agents. Following the treatment, you should avoid direct sunlight for at least 48 hours, including exposure through windows.