The Medical Letter on Drugs and Therapeutics
Sunscreens: An Update
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Sunscreens are an important component of photoprotection. A new definition of their effectiveness has been proposed, and some issues have arisen concerning their safety.

UVA and UVB — Solar UV radiation capable of injuring the skin is classified by wavelength into UVA1 (340-400 nm), UVA2 (320-340 nm) and UVB (290-320 nm). UVA, which makes up 95% of terrestrial UV radiation and penetrates into the dermis, causes long-term sun damage. UVB, which is mostly absorbed in the epidermis, is largely responsible for the erythema of sunburn (UVA2 is also erythemogenic). Both UVA and UVB can cause photoaging, suppress immune function and cause skin cancer.1,2 UVB is present primarily in late spring, summer and early autumn in temperate climates and is strongest at midday. UVA is more constant throughout the day and the year and, unlike UVB, is not filtered by clear ... more      

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Title: Sunscreens: An Update
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