The skin is damaged by ultraviolet (UV) radiation from the Sun. Shorter wavelength (UV-B) rays have more energy and are more damaging, but both UV-B and UV-A rays can cause burns, skin cancer and premature aging. To avoid this, lotions with chemical solar filters such as PABA (para-amino benzoic acid), cinnamic acid, sulfonic acid or camphor are used, which absorb UV radiation. Different concentrations of these sutancias lotion determine the protection factor of the skin (SPF, which stands for skin protection factor). SPF values range from 2 to 50. The number measures how many more times you can be in the sun without getting burned than if you hadn't used sunscreen. For example, an SPF 15 means that you can stay in the sun 15 times longer. It is estimated that normal skin can be safely exposed to the sun for 20 minutes .
Most doctors recommend a sun protection factor level of 30 or higher . SPF values above 50 have not been shown to offer better protection than a product with an SPF 50.
