Skin Injuries: Mechanical, Thermal, Chemical and Radiation Injuries. Photodermatoses

Skin damage can be caused by a variety of physical agents in the external environment, including mechanical and thermal injury, radiation (ionizing and nonionizing), electricity, and extreme temperatures. The degree of skin damage depends on the type of agent, the amount and duration of exposure, the area of skin exposed, and the ability of the defense mechanisms of the skin. Ultraviolet (UV) radiation is responsible for a variety of acute and chronic skin damage. The most common acute effect of UV on the skin is the induction of inflammation. Excessive exposure to UV leads to skin atrophy, pigmentation, immunosuppression, photoaging, and increased risk of skin malignancies. Photodermatoses are skin disorders characterized by abnormal reactions to ultraviolet radiation, visible light, and infrared radiation from the sun or artificial sources. The main classifications of photodermatoses include idiopathic photodermatoses, photodermatoses caused by exogenous or endogenous factors, photosensitive dermatoses, and genetic photodermatoses.