Mechanisms of photodamage of the skin and its functional consequences for skin ageing.

Chronic photodamage of the skin manifests itself as extrinsic skin ageing (photoageing) and photocarcinogenesis. DNA photodamage and UV-generated reactive oxygen species are the initial molecular events that lead to most of the typical histological and clinical manifestations of chronic photodamage of the skin. Knowledge of the UV-absorbing chromophores in the skin and of the molecular mechanisms leading to the unwanted effects of sun exposure provide a basis for the development of novel strategies for the prevention and repair of photoageing. This review provides an overview of the photochemistry of the major skin chromophores and their relationship to chronic photodamage.