Sunscreen (also known as sunblock, or sun cream) is a photo-protective topical product that helps prevent skin damage from ultraviolet (UV) radiation emitted by the sun. It reduces sunburn and other skin damage, with the goal lowering your risk of skin cancer.
The most effective sunscreens protect against both UVB (ultraviolet radiation with wavelength between 290 and 320 nanometres), which can cause sunburn, and UVA (between 320 and 400 nanometres), which damages the skin with more long-term effects, such as premature skin aging. Most sunscreens work by containing either a petrochemical compound that absorbs ultraviolet light (such as oxybenzone) or minerals that reflects light (such as titanium dioxide, zinc oxide), or a combination of both.
Sunscreen is regulated as an OTC product by the FDA. Most sunscreens are not considered reef safe as they use petrochemicals. As such the use of petrochemical based sunscreen has been banned in ecological and progressive area's, such as, Mexico's Marine Reserves, the State of Hawaii, Aruba, Thailand's National Park areas, the Marshal Islands.