In normal, unstressed cells, there is a constant production of
reactive oxygen from the mitochondria, which is balanced by the
production of antioxidant enzymes in the cell, such as superoxide
dismutase (SOD), catalase, and glutathione peroxidase. When
a cell comes under stress, this balance is interrupted, and the reactive
oxygen species can overwhelm the cells and lead to a change
in normal cellular behaviors. Oxidative stress can be generated
by a variety of factors, including cigarette smoke, extreme
temperature change, and exposure to UV radiation. Exposure
to UV radiation is one of the most important factors in many
skin disorders and diseases, including aging and cancer.
There are three main types of UV radiation; UVA, UVB, and UVC.
UVA is the longest wavelength and is thought to be responsible for
many skin conditions including skin aging and skin carcinogenesis