Several active ingredients found in different sunscreens enter the bloodstream at levels that far exceed the FDA's recommended threshold without a government safety inspection, a new study in Journal of the American Medical Association suggests.

Leading dermatologists who reviewed the new findings for Practical Dermatology® magazine are quick to caution that the benefits of using sunscreen far exceed any downsides.

“Ultraviolet radiation causes skin cancer. Therefore a comprehensive sun protective regimen which includes sunscreen, sun avoidance and protective clothing is central to prevention,” says Adam Friedman, MD, FAAD, Professor and Interim Chair of Dermatology at George Washington School of Medicine and Health Sciences in Washington, DC, where he also serves as  Residency Program Director, Director of Translational Research and Director of Supportive Oncodermatology.

In the study, 24 participants applied 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 avobenzone, oxybenzone, octocrylene and ecamsule. If the blood absorption of any of these ingredients exceeds 0.5 nanograms per milliliter (ng/mL), the FDA recommends that they undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies.

The levels of all four chemicals in the participants’ bloodstreams far exceeded that even within one day — and three remained there for seven days. For oxybenzone, in particular, plasma concentrations reached the threshold within two hours after a single application and exceeded 20 ng/mL on day 7 of the study. The FDA has previously included these four chemicals on a list of ingredients that need to be researched further before they can be considered “generally safe and effective.”

(Hawaii, the Pacific nation of Palau, and Florida's Key West recently banned sunscreens containing oxybenzone and octinoxate because they cause coral bleaching and are dangerous to marine life.)

 “These data do not suggest that individuals should refrain from using sunscreen,” stresses Dr. Friedman. “While these data certainly suggest that the systemic absorption of sunscreens should be evaluated, these findings cannot be correlated to toxicity or pathology.” Furthermore, he says, the experimental protocol was for optimal use which is not the same as real-world use.

Moreover, the number of those evaluated was low (six per group) and did not account for all skin types and external environments which do play a role in barrier integrity, Dr. Friedman says.

Joshua Zeichner, MD, Director of Cosmetic and Clinical Research in the Department of Dermatology at The Mount Sinai Hospital in New York City, agrees. “In the real world, consumers do not apply as much sunscreen as they should or reapply every two hours so it is unclear whether there is absorption with every day, real-world use.”

More data is clearly needed, he says. “Based on what we know today, the benefit of wearing sunscreen in protecting the skin against skin cancer and premature aging outweighs the potential risks.”

Alternatives to these chemical blockers do exist. “If anyone is concerned with the use of chemical blocker sunscreens, mineral options that contain zinc oxide alone or in combination with titanium dioxide are a great option.”

“These sunscreen ingredients have been used for several decades without any reported internal side effects in humans,” adds AAD President George J. Hruza in a statement. “Skin cancer is the most common cancer in the United States, and dermatologists see the impact it has on patients’ lives every day. Unprotected exposure to the sun’s ultraviolet rays is a major risk factor for skin cancer.”