Sun Protection

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A few months ago, just in time for summer, there were several media stories of how a study had found that some ingredients in sunscreens were found in the bloodstreams of study participants. These media stories somehow appeared before the actual study they were based on was published. That study, which appeared in the June 4, 2019 edition of the Journal of the American Medical Association, was not the first study to find this phenomenon. It has been known for years that chemicals in sunscreens can be found in the blood. In fact, the FDA sunscreen guidance rule is that they should not appear in the blood at levels above 0.5 ng/mL (nanograms per milliliter). The June 4 study found levels above the FDA guidelines, but the study methods were less than realistic.

Sunscreens work by reflecting, absorbing, and/or scattering UV radiation and are regulated as OTC (over the counter) products here in the U.S. They should not be confused with sunblocks. Sunblocks, usually made of zinc or titanium oxide, prevent sunlight from reaching the skin. Sunblock ingredients are not absorbed by the body. The June study’s objective was to determine the amount of absorption of four commercially available sunscreen ingredients. Each sunscreen contained a different active ingredient. These active ingredients were avobenzone, oxybenzone, octocrylene, and ecamsule.

The study looked at the absorption of the ingredients under “maximal usage conditions.” These conditions followed the re-application instructions found on the labels. Most sunscreen labels recommend re-application every two hours. This is because the products may be washed off the skin by immersion in water and by sweating, by clothing or towels, and by other activities by the person using the product. The study did reapply the products every two hours, but to all of the body not covered by a bathing suit. In addition, it was done indoors with no immersion in water and no activity by the participants, meaning no sweating and no toweling off. Given these unrealistic conditions, it is not surprising that the products were found in the bloodstreams of the study subjects in levels exceeding the FDA recommendations. Additionally, the study did not take into account the skin type, skin color, or age of the participant. These factors may alter the rates of product absorption.

The study’s authors did acknowledge these study limitations. They also admitted that additional research is needed, especially into what the ramifications of absorption of these products actually are. While it has been known for some time that these products can be absorbed, no one as yet knows whether there are any risks or harms from absorbing these products. Lastly, the authors noted that given the fact that skin cancer is by far the most common cancer in this country and its rates are growing, the results of their study should not deter anyone from using sunscreen (or sunblock).

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