Sunscreen labels

This article is the archived version of a report that appeared in July 2009 Consumer Reports magazine.

UVA

Ultraviolet A radiation. Penetrating rays that can cause sunburn, wrinkles, and age spots and contribute to skin cancer.

UVB

Ultraviolet B radiation. Can cause sunburn and other skin damage and contribute to skin cancer.

SPF

Sun-protection factor, a measure of UVB sunburn protection on treated skin as compared with untreated skin. (Put simply, if skin normally takes 10 minutes to turn red, SPF 30 lengthens that time to about 300 minutes.)

Broad spectrum

Implies that the product blocks UVA and UVB radiation, but doesn't indicate how effective the blocking is.

PABA-free

Contains no esters of para-aminobenzoic acid, an older sunblocking ingredient that caused allergic reactions. Few if any products in the U.S. use PABA anymore.

Water resistant

Maintains the claimed SPF after 40 minutes in water.

Very water resistant

Maintains the claimed SPF after 80 minutes in water. "Waterproof" has no FDA-accepted definition, but some manufacturers use it to mean very water resistant.

Nanoparticles

Manufactured microscopic particles of a material that might behave differently—chemically or physically—from regular-sized particles. In sunscreens, zinc oxide and titanium dioxide, mineral-based white pigments, are often used nano-sized, in part to make them look clearer on skin. Scientific studies have raised concerns about potential adverse effects of nanoscale ingredients in sunscreens and other products on human and environmental health, but manufacturers aren't required to disclose the use of nanoparticles. For more on the subject, go to www.ConsumerReportsHealth.org and search on "nanotechnology."