EVANSTON, Ill. (WLS) -- Nearly half of all sunscreens don't work like they're supposed to, according to a study just released by Northwestern University.
The study, which looked at 65 top-rated sunscreens on Amazon.com, found about 40 percent of them didn't meet guidelines set by the American Academy of Dermatology.
Researchers said the most glaring issue is that the sunscreens weren't water or sweat-resistant.
The purpose of the study was to identify high-performing sunscreens that are affordable and easy to use.
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Many top-selling sunscreens don't offer adequate protection, study says