Sun Protection Factor SPF

Sunscreen products are labeled with a sun protection factor (SPF), which is a measure of how effectively the sunscreen works; the higher the number, the more the protection (up to about SPF 30; after that, there is not much additional protection). Sunscreen should have a minimum SPF of 15; an SPF of 15 means that children using the sunscreen could spend up to 15 times longer in the sun without burning than if they were not wearing it. However, the SPF applies only to UVB; no rating for UvA currently exists.

An SPF 15 blocks 94 percent of UVB rays, an SPF 30 blocks 98 percent, and an SPF 50 also blocks 98 percent of the UvB rays. So even if you do not burn, you will still be exposed to some UvB rays. And since some people skimp when applying sunscreen, or apply it unevenly, experts rationalize that if you skimp when applying SF 15 you might end up with the equivalent of an SP 6, whereas if you skimp using an SPF of 50, you'll still get adequate protection.

However, the FDA established guidelines for safety of sunscreens in 1978; they are currently revising sunscreen labeling to include a maximum

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