摘要：Among harmful environmental factors that contribute to extrinsic aging, long-term effects of repeated exposure to ultraviolet light are the most significant and are referred to as photoaging. Photoaging is a multisystem degenerative process that involves the skin and skin support system. It is a cumulative process and depends primarily on the degree of sun exposure and skin pigment. The epidermis and dermis are both affected by UVB, but the dermis is also affected to a significant extent by UVA. It has long been thought that the majority of human photo-lesions due to UVB rays, now it is believed that UVA play a substantial role in photoaging. Photoaging affects the sun-exposed areas and is characterized clinically by fine and coarse wrinkling, roughness, dryness, laxity, teleangiectasia, loss of tensile strength and pigmentary changes. There is also an increase in development of benign and malignant neoplasms on photoaged skin. During the years the progress has been made in understanding the photoaging in human skin. UV irradiation invokes a complex sequence of specific molecular responses that damage skin connective tissue. Restriction of UV irradiation and the use of high-protection, broad-spectrum sunscreens may slow progression of photoaging.
