The sun sends out different types of radiation that reach the earth –visible light that is seen as sunlight, infrared radiation which can be felt as heat and ultraviolet radiation (UVR), that we can’t see. Ultraviolet radiation can be classified as UVA, UVB, or UVC. The ozone layer absorbs some, but not all, of these types of UV radiation. UVA rays account for up to 95% of the UV radiation reaching the earth’s surface, and can penetrate through clouds and glass. These UVA rays play a major part in photodamage and skin ageing, while UVB rays are the main cause of skin reddening and sunburn, damage which can lead to premature skin ageing.
Both UVA and UVB rays have the potential to cause skin cancers. Skin cancer is a disease of the body's skin cells and occurs when skin cells are damaged by UV radiation penetrating the skin. UV damages skin cell DNA, causing cells to mutate and grow abnormally. If these mutant cells are not destroyed through the body’s own processes or other means, they will continue to develop into skin cancers.