npr:

When we smear on sunscreen, dermatologist Kanade Shinkai with the University of California, San Francisco says, most of us don’t think about it getting under our skin.

“I think there was an assumption that these are things that we apply to our skin — they don’t really get into our bloodstream,” Shinkai says.

But earlier this year, the Food and Drug Administration raised concerns about chemicals commonly found in sunscreen, noting that they can enter the bloodstream at levels significantly higher than the current FDA threshold for safety testing. And it’s unknown whether there are any harmful health effects. So the agency has asked sunscreen manufacturers to complete safety studies by this November.

The FDA noted that only two of the 16 active ingredients commonly used in commercial sunscreens — the mineral sunblocks, zinc oxide and titanium dioxide — are “generally recognized as safe and effective.” That’s a designation the FDA gives a substance when qualified experts consider it generally safe for its intended use.

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