Photodynamic therapy (PDT) is a procedure in which we apply a special medicine, called photosensitizer, to problematic skin areas and then expose the area of concern under blue light or another light source to activate the photosensitizer to treat entire affected areas efficiently. We perform PDT frequently in our clinic for pre-cancerous lesions, superficial cancers and acne. Dr. Connie Nguyen has given lecture on PDT. One should stay out of the direct light for 2-7 days after a PDT session. Repeated treatments may be necessary to optimal results depending on the severity of the conditions.