Photodermatology and Photomedicine: UV Biology, Photoprotection, and Phototherapy

This chapter reviews the molecular and cellular mechanisms underlying UV-induced skin injury, photocarcinogenesis, and photoimmunology, integrating recent discoveries in DNA damage response and repair pathways. It examines advances in phototherapy — including narrowband UVB, PUVA, and targeted photodynamic therapy — across inflammatory, neoplastic, and pigmentary dermatoses, with attention to optimizing treatment protocols and minimizing long-term risks. The chapter also covers the evolving science of photoprotection, including next-generation sunscreen formulations, antioxidant strategies, and the contentious relationship between UV exposure, vitamin D synthesis, and immune regulation.