Human skin, like all other organs, undergoes chronological aging. In addition, unlike other
organs, skin is in direct contact with the environment and therefore undergoes aging as a
consequence of environmental damage. The primary environmental factor that causes
human skin aging is UV irradiation from the sun. This sun-induced skin aging (photoaging),
like chronological aging, is a cumulative process. However, unlike chronological aging,
which depends on the passage of time per se, photoaging depends primarily on the degree …