Skin Photoaging (SP)
Photoaging or photoageing (also known as "dermatoheliosis") is a term used for the characteristic changes to skin induced by chronic UVA and UVB exposure.:29 Tretinoin is the best studied retinoid in the treatment of photoaging. The deterioration of biological functions and ability to manage metabolic stress is one of the major consequences of the aging process. Aging is a complex, progressive process that leads to functional and esthetic changes in the skin. This process can result from both intrinsic (i.e., genetically determined) as well as extrinsic processes (i.e., environmental factors). Photoaging is attributed to continuous, long-term exposure to ultraviolet (UV) radiation of approximately 300–400 nm, either natural or synthetic, on an intrinsically aged skin.