Sunscreen ingredients soak all the way into your blood. The question remains, is that safe?

Whether you’re basking in the winter sun or generally have a schedule that demands you to step outdoors quite often—one thing that you have to make sure is that you are well-protected by a sunscreen.

Sunscreens sure protect our skin from the harmful UV rays, but researchers at the U.S. Food and Drug Administration have shown that active chemicals in sunscreens can readily seep into the bloodstream, confirming the need for more testing on whether these products are safe or not.

The study, published in the Journal of the American Medical Association, replicates findings of a pilot study by FDA scientists in May, which raised a number of questions over the safety of sunscreens, Dr. Adam Friedman, chairman of dermatology at George Washington University, told Reuters in a telephonic interview.

For the study, six chemical sunscreen ingredients were tested on 48 people. The ingredients were from four commercially available formulations—three sprays and one lotion.

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The participants were asked to apply the sunscreens over 75% of their body once on the first day, then four times a day for three more days.

The study aimed to determine whether common sunscreen ingredients exceeded 0.5 nanograms per milliliter of blood. FDA recommends that products exceeding that threshold be tested for safety. Of the six tested, all reached blood concentrations that exceeded the limit.

However, the researchers also stressed that their findings don’t suggest that people should stop using sunscreen.

“It was completely misinterpreted,” said Friedman, who was not involved with the study. “Just because it’s in the blood doesn’t mean that is not safe. It doesn’t mean it’s safe either. The answer is we don’t know.”

As per a rule proposed by the FDA, sunscreen manufacturers need to provide additional information on the active ingredients in their products.

“Results of our study released today show there is evidence that some sunscreen active ingredients may be absorbed,” Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, said in a statement.

Woodcock said the study emphasizes the need for sunscreen makers to test whether their products are safe when absorbed into the bloodstream.

The FDA has already certified that sunscreens that block the sun’s rays with minerals – such as zinc oxide and titanium dioxide – are safe, but these often leave residue on the skin.

(Reporting by Julie Steenhuysen)