Environmental influences on skin aging and ethnic-specific manifestations

Skin aging does not only occur by passing time alone but also by the exposure to different environmental factors. The skin aging process, which is induced by environmental factors, is named premature or extrinsic skin aging process and can be distinguished from the chronologically (intrinsic) skin aging process by characteristic skin aging signs. Well known environmental factors leading to extrinsic skin aging are sun exposure and smoking. Recently, an epidemiological study could further discover an association between air pollution and skin aging. First of all the skin aging inducing effect of sun exposure was discovered and an own term (photoaging) was given to this special field of extrinsic skin aging. Mechanistic studies have further increased our knowledge about the molecular pathways by which environmental factors contribute to extrinsic skin aging. In this regard, profound knowledge how sun exposure leads to extrinsic skin aging were gained in the last years, and additionally there are also indications how smoking and air pollution might contribute to this process. Moreover it was realized that extrinsic skin aging manifests differently between different populations. Thus, in this review we summarize the influence of the different environmental factors: sun exposure, smoking and air pollution on skin aging and further present ethnic-specific manifestations of extrinsic skin aging.