(LOS ANGELES) -- SPF, or sun protection factor, is associated with sunscreens that help block UVB rays, according to the LA Times.
Sunburns are caused by UVB rays. The SPF rating is the ratio of time you should be protected from the sun before getting a sun burn. For example, theoretically if you use a SPF 15, it should take 15 times longer to get a sun burn than if you did not use sunscreen.
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