FDA study finds sunscreen's active ingredients readily absorbed in bloodstream

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The active chemicals in sunscreens can readily soak into the bloodstream, found a US Food and Drug Administration pilot study.

Scientists at the US Food and Drug Administration have shown that active chemicals in sunscreens can readily soak into the bloodstream, confirming the need for more testing on whether these products are safe, Reuters Health reports researchers said. The study replicates findings of a pilot study by FDA scientists in May. That touched off a flurry of questions over the safety of sunscreens, Dr Adam Friedman, chair of dermatology at George Washington University, said. “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.”

The FDA has proposed a rule requiring sunscreen manufacturers to provide additional information on the active ingredients in their products.

The study authors stressed that their findings do not suggest that people should stop using sunscreen.

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

“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 Centre for Drug Evaluation and Research, said. Woodcock said the study emphasises 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.

Importance: A prior pilot study demonstrated the systemic absorption of 4 sunscreen active ingredients; additional studies are needed to determine the systemic absorption of additional active ingredients and how quickly systemic exposure exceeds 0.5 ng/mL as recommended by the US Food and Drug Administration (FDA).
Objective: To assess the systemic absorption and pharmacokinetics of the 6 active ingredients (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate) in 4 sunscreen products under single- and maximal-use conditions.

Design, Setting, and Participants: Randomized clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) was conducted in 48 healthy participants. The study was conducted between January and February 2019.
Interventions: Participants were randomized to 1 of 4 sunscreen products, formulated as lotion (n = 12), aerosol spray (n = 12), nonaerosol spray (n = 12), and pump spray (n = 12). Sunscreen product was applied at 2 mg/cm2 to 75% of body surface area at 0 hours on day 1 and 4 times on day 2 through day 4 at 2-hour intervals, and 34 blood samples were collected over 21 days from each participant.

Main Outcomes and Measures: The primary outcome was the maximum plasma concentration of avobenzone over days 1 through 21. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, homosalate, octisalate, and octinoxate over days 1 through 21.
Results: Among 48 randomized participants (mean [SD] age, 38.7 [13.2] years; 24 women [50%]; 23 white [48%], 23 African American [48%], 1 Asian [2%], and 1 of unknown race/ethnicity [2%]), 44 (92%) completed the trial. Geometric mean maximum plasma concentrations of all 6 active ingredients were greater than 0.5 ng/mL, and this threshold was surpassed on day 1 after a single application for all active ingredients. For avobenzone, the overall maximum plasma concentrations were 7.1 ng/mL (coefficient of variation [CV], 73.9%) for lotion, 3.5 ng/mL (CV, 70.9%) for aerosol spray, 3.5 ng/mL (CV, 73.0%) for nonaerosol spray, and 3.3 ng/mL (CV, 47.8%) for pump spray. For oxybenzone, the concentrations were 258.1 ng/mL (CV, 53.0%) for lotion and 180.1 ng/mL (CV, 57.3%) for aerosol spray. For octocrylene, the concentrations were 7.8 ng/mL (CV, 87.1%) for lotion, 6.6 ng/mL (CV, 78.1%) for aerosol spray, and 6.6 ng/mL (CV, 103.9%) for nonaerosol spray. For homosalate, concentrations were 23.1 ng/mL (CV, 68.0%) for aerosol spray, 17.9 ng/mL (CV, 61.7%) for nonaerosol spray, and 13.9 ng/mL (CV, 70.2%) for pump spray. For octisalate, concentrations were 5.1 ng/mL (CV, 81.6%) for aerosol spray, 5.8 ng/mL (CV, 77.4%) for nonaerosol spray, and 4.6 ng/mL (CV, 97.6%) for pump spray. For octinoxate, concentrations were 7.9 ng/mL (CV, 86.5%) for nonaerosol spray and 5.2 ng/mL (CV, 68.2%) for pump spray. The most common adverse event was rash, which developed in 14 participants.

Conclusions and Relevance: In this study conducted in a clinical pharmacology unit and examining sunscreen application among healthy participants, all 6 of the tested active ingredients administered in 4 different sunscreen formulations were systemically absorbed and had plasma concentrations that surpassed the FDA threshold for potentially waiving some of the additional safety studies for sunscreens. These findings do not indicate that individuals should refrain from the use of sunscreen.

Murali K Matta; Jeffry Florian; Robbert Zusterzeel; Nageswara R Pilli; Vikram Patal; Donna A Volpe; Yang Yang; Luke Oh; Edward Brashaw; Issam Zineh; Carlos Sanabria; Sarah Kemp; Anthony Godfrey; Steven Adah; Sergia Coelho; Jian Wang; Lesley-Anne Furlong; Charles Ganley; Theresa Michele; David G Strauss

Reuters Health report

JAMA abstract

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