What Is Sunscreen And How It Works?

Sunscreen is any substance or material that protects the skin from ultra violet radiation. Sunscreens are available in the forms of topical lotion, cream, ointment, gel, or spray that can be applied to the skin; a salve or stick that can be applied to the lips, nose, and eyelids; a moistener in towels that can be rubbed against the skin; sunglasses that protect the eyes; and film screen that can be affixed to the windows of a car, room, or office.

The best sunscreens protect against both UVB, which can cause sunburn, and UVA, which damages the skin with more long-term effects such as premature skin aging. Most sunscreens work by containing either an organic chemical compound that absorbs ultraviolet light or an opaque material that reflects light, or a combination of both. Typically, absorptive materials are referred to as chemical blocks, whereas opaque materials are mineral or physical blocks.

SPF, an abbreviation for sun-protection factor, is a number such as that indicates how long a topical sunscreen remains effective on the skin. A user can determine the duration of effectiveness simply by multiplying the SPF by the length of time to cause a burn without sunscreen.