PDT is used to treat actinic keratoses, acne, photoaging and skin cancer. His research involves sun protection, photoaging, collagen chemistry, and topical percutaneous absorption of antioxidants. Adapalene has not been widely studied or proven for use in photoaging. Because of this, extrinsic aging is often referred to as photoaging. A 5% ecamsule containing sunscreen can prevent early changes leading to photoaging in humans. Sun protection is the most effective form of primary prevention of photoaging. Tazarotene is been proven to be efficiacious in the treatment of photoaging. Photoaging may be defined as skin changes caused by chronic exposure to UV light.