When people use sunscreen heavily, tiny amounts of its chemicals—avobenzone and oxybenzone—can get into their blood, and scientists can measure these tiny amounts, though they’re way too small to see or feel.

When people use sunscreen all over their body as much as possible, their blood ends up with a lot of oxybenzone—over 200 nanograms per milliliter—while other sunscreen chemicals like avobenzone and octocrylene show up too, but in much smaller amounts.

When people use sunscreen heavily—covering most of their skin and reapplying it four times a day for four days—chemicals in the sunscreen get into their bloodstream at levels higher than what the FDA says should trigger safety checks.

When you put on sunscreen with chemicals like oxybenzone or avobenzone, your body absorbs more of those chemicals into your bloodstream than the FDA thinks is safe — even if you just use it normally on your skin.

When you slather on sunscreen with certain chemicals like oxybenzone or avobenzone really thickly over most of your body, your body absorbs a tiny bit of those chemicals into your bloodstream—so much that it crosses a safety alert level set by the FDA, which says, 'Hey, we need to study this more.'

When people use sunscreen heavily, oxybenzone—a common ingredient—gets into the bloodstream more than other sunscreen chemicals, reaching levels more than 500 times higher than what the FDA considers worth checking for safety.