The sun is a powerful source of energy and radiation that can be both beneficial and harmful. It feels so great to get out in the sun, especially after a cold, rainy day, but the effects of too much sun can be incredibly damaging to skin health. The sunlight’s cellular and molecular effects depend on the radiation energy and penetration. The spectrum of solar radiation ranges from the shorter wavelengths of UVB and UVA to the longer wavelengths of visible radiation (VIS), near-infrared radiation (NIR) and infrared radiation (IR). UV radiation has more energy and is more penetrating. UVB radiation has more energy than UVA radiation.
UVA exposure, however, causes accelerated skin aging known as photoaging or extrinsic aging (as opposed to normal or instrinsic aging). Photo-aged skin is characterized by deep wrinkling, loss of elasticity, uneven pigmentation, dryness, and rough texture. The UV-induced degeneration of skin is a cumulative process that depends on the frequency, duration and intensity of exposure, as well as skin pigmentation. UV radiation and NIR radiation both give rise to the generation of reactive oxygen species (ROS). ROS play an important role in skin aging due to the fact that aged skin has a decreased ability to neutralize ROS leading to increased oxidative stress. Continue reading