Are serum elevations of topically applied sunscreen ingredients relevant?
Six active in a randomized trial including four product types. The results were published in JAMA.
The testing was done as part of a proposed rule on sunscreen, published in February 2019, which requested additional information on sunscreen ingredients. Murali K. Matta, PhD, of the Food and Drug Administration and coauthors wrote that these plasma concentrations “surpassed the FDA threshold for potentially waiving additional safety studies for sunscreens.” But, they added, the findings “do not indicate that individuals should refrain from the use of sunscreen.”
This was a follow-up study to a smaller study of 24 health volunteers published last year that determined that the sunscreen active ingredients tested were absorbed systemically (JAMA. 2019;321[21]:2082-91). “This follow-up study expanded the sample size, tested additional sunscreen active ingredients and formulations, and confirmed the finding that sunscreen active ingredients are systemically absorbed,” the authors wrote.
To gather information on the absorption of active ingredients in sunscreens, the investigators randomized 48 adults to one of four sunscreen products (lotion, aerosol spray, nonaerosol spray, or pump spray) with one of six active ingredients (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate). Not all products contained each of the ingredients.
The participants applied the products in amounts of 2 mg/cm2 to 75% of body surface area at baseline, no use on day 1 and four times a day at 2-hour intervals on days 2 through 4. The researchers collected blood samples over 21 days and measured the maximum plasma concentrations. The average age of the participants was 37 years, and half were women. The study was conducted in a clinical pharmacology unit.
The geometric mean maximum plasma concentrations for the primary endpoint of avobenzone in lotion, aerosol spray, nonaerosol spray, and pump spray were 7.1 ng/mL, 3.5 ng/mL, 3.5 ng/mL, and 3.3 ng/mL, respectively.
For oxybenzone, the concentrations were 258.1 ng/mL and 180.1 ng/mL, respectively, for lotion and aerosol spray. The concentrations for octocrylene were 7.8 ng/mL, 6.6 ng/mL, and 6.6 ng/mL, respectively, for lotion, aerosol spray, and nonaerosol spray.
For homosalate, the geometric mean plasma concentrations were 23.1 ng/mL for aerosol spray, 17.9 for nonaerosol spray, and 13.9 for pump spray. For octisalate, the concentrations were 5.1 ng/mL, 5.8 ng/mL, and 4.6 ng/mL, respectively, for aerosol spray, nonaerosol spray, and pump spray. For octinoxate, the concentrations were 7.9 ng/mL for nonaerosol spray and 5.2 ng/mL for pump spray.
“The systemic exposures, as measured by geometric mean maximum plasma concentrations, of all the tested active ingredients were higher than 0.5 ng/mL after a single application,” the researchers noted.
Overall, the most common event was rash, which was reported in 14 participants.
The study findings were limited by several factors including the use of an indoor clinical setting, rather than outdoor exposure; the inability to assess absorption differences by formulation and Fitzpatrick skin type; and the variation in amounts of ingredients among products, the researchers noted. However, the results can be used to design additional studies needed to research the effects of systemic exposure to sunscreen ingredients, they said.
In an accompanying editorial (JAMA. 2020;323:223-4), Adewole S. Adamson, MD, of the University of Texas at Austin, and Kanade Shinkai, MD, of the University of California, San Francisco, wrote that “the study did not address key questions about sunscreen safety,” including the length of time it takes “for plasma concentrations of sunscreen ingredients to fall below the FDA threshold for safety testing.” Dr. Shinkai is also editor in chief of JAMA Dermatology.
“In making an informed decision, clinicians must determine whether the magnitude of the benefit exceeds the risk of potential harm for a specific individual,” they said. “Importantly, this balance may be different, depending on characteristics of the sunscreen user (e.g., for individuals with darker skin types and for children) and may depend on the frequency and duration of application (e.g., daily vs. intermittent use; starting in infancy or later in life),” they noted.
“In the absence of clear data demonstrating harm, the use of chemical sunscreen may still be considered appropriate; the use of mineral-based sunscreen is a well-established safe alternative,” although the potential harms remain uncertain until the sunscreen industry conducts the safety studies recommended by the FDA, Dr. Adamson and Dr. Shinkai concluded.
In a statement released by the FDA on Jan 21, the day the study was published, Janet Woodcock, MD, director of the FDA’s Center for Drug Evaluation and Research, said that, considering the “recognized public health benefits” of using sunscreen, the FDA “urges Americans to use sunscreens in conjunction with other sun protective measures (such as protective clothing).”
Commenting on the study, she said, “results from our study released today show there is evidence that some sunscreen active ingredients may be absorbed. However, the fact that an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate such. Rather, this finding calls for further industry testing to determine the safety and effect of systemic exposure of sunscreen ingredients, especially with chronic use.”
The study was supported by the FDA. The researchers and editorial authors had no financial conflicts to disclose.
SOURCES: Matta MK et al. JAMA. 2020;323:256-267.