Mechanisms and Treatment of Photoaging and Photodamage

Damage caused by excessive, long-term sun exposure contributes to signs of ageing and is most readily recognizable on our external surface, the skin. The damaging effects of the sun are mainly caused by ultraviolet radiation (UVR) which, on earth, consists of UVA (320 to 400 nm) and UVB (280 to 320 nm). The third type of UV radiation, UVC, also called short‐ wave or ionizing radiation, is absorbed by gasses in our atmosphere, does not reach the earth’s surface and does not normally contribute to photodamage of skin. Ozone is one of the gases that absorbs UVC – fortunately, since UVC’s ionizing effects can significantly alter cellular structures and molecules. Although UVB and UVA radiation does not have enough energy to ionize atoms, it can alter chemical bonds in molecules, thus altering their structure and functions. Skin cells are particularly susceptible to alterations mediated principally by the creation of free radicals and oxidative stress and changes in DNA structure can result in constitutive expression of protocongenes and ultimately the development of cancerous skin lesions.