Sunscreen

A topical preparation that absorbs, reflects, or scatters ultraviolet radiation to reduce its effects on skin. Its protection is measured against defined UV exposures and depends on how it is applied.

Ultraviolet: Electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays. Sunscreen is designed to reduce exposure to ultraviolet wavelengths reaching the skin.
Organic ultraviolet filters: Carbon-based sunscreen ingredients that absorb ultraviolet radiation and release its energy through molecular processes. These filters provide much of sunscreen's UV absorption and include ingredients such as avobenzone.
Sunburn: An inflammatory skin injury caused mainly by excessive ultraviolet radiation, especially UVB. Preventing sunburn is the outcome most directly represented by SPF.
Sun avoidance: Reducing exposure to sunlight by seeking shade or limiting time outdoors. Avoiding intense exposure reduces UV dose without relying on a topical product.
Ultraviolet A: Ultraviolet radiation with wavelengths from about 315 to 400 nanometers. UVA penetrates deeply into skin, so broad-spectrum products must address it as well as UVB.
Inorganic ultraviolet filters: Mineral sunscreen ingredients, chiefly zinc oxide and titanium dioxide, that attenuate ultraviolet radiation. These particulate filters are often called mineral or physical sunscreen ingredients.
Photoaging: Premature skin changes caused by chronic exposure to ultraviolet and other environmental radiation. Consistent sunscreen use helps limit UV-driven wrinkles, pigment changes, and loss of skin elasticity.
Ultraviolet index: A scale communicating the strength of sunburn-producing ultraviolet radiation at a particular time and place. It helps relate sunscreen use to changing environmental UV intensity.
Ultraviolet B: Ultraviolet radiation with wavelengths from about 280 to 315 nanometers. UVB causes sunburn and is the main radiation used to determine a sunscreen's SPF.
Avobenzone: An organic ultraviolet filter that absorbs UVA radiation and is used in sunscreens. It is a common UVA filter whose stability in formulations can require attention.

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