The chemicals in sunscreen don't just sit on top of the skin, they absorb in the bloodstream, according to new research from the U.S. Food and Drug Administration.

A study published Monday in the peer-reviewed medical journal JAMA found that several active ingredients in different sunscreens enter the bloodstream at levels that far exceed the FDA's recommended threshold without a government safety inspection.

“However, sunscreens have not been subjected to standard drug safety testing, and clinicians and consumers lack data on systemic drug levels despite decades of widespread use," former FDA chairman Robert Califf and JAMA Dermatology Editor in Chief Kanade Shinkai wrote in an editorial accompanying the study.

The 24 participants in the study were instructed to apply one of four different kinds of sunscreen spray, lotion or cream four times per day for four days on all areas that wouldn’t be covered by a swimsuit.

Researchers then measured the concentration of four different active ingredients in the participants’ blood: avobenzone, oxybenzone, octocrylene and ecamsule. If the absorption exceeds 0.5 ng/mL, the FDA recommends “nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies.”

For all ingredients, the levels of all chemicals far exceeded that limit on the first day of the study. Three of the ingredients remained in the bloodstream for seven days. For oxybenzone, which has been found along with other sunscreen ingredients in breast milk, plasma concentrations reached the threshold within two hours after a single application and exceeded 20 ng/mL on day 7 of the study.

Oxybenzone is also believed by scientists to be toxic to coral reefs, which has led Hawaii to ban sunscreens that contain it.

The FDA has previously included those four chemicals on a list of ingredients that need to be researched further before they can be considered generally safe and effective.

Other sun-protective options include staying indoors and wearing sun-protective clothing. Clothing manufacturers have recently begun to make lightweight long sleeve shirts that are breathable but have been shown to be effective at reflecting the sun’s harmful rays and exposing less of the body to direct sunlight, reducing the need for a sunscreen product.

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