Active ingredients in varying sunscreen formulations are absorbed in measurable plasma concentrations that exceed US Food and Drug Administration (FDA) thresholds, according to the results of a study published in JAMA. The authors note that further investigations are required to assess the clinical significance of the study findings.
Investigators conducted a randomized clinical trial to determine absorption and pharmacokinetics of 6 active ingredients (avobenzone, oxybenzone, oxtocrylene, homosalate, octisalate, and oxtinoxate) of 4 types of sunscreens (lotion, aerosol spray, nonaerosol spray, and pump spray). The sunscreens were studied under single- or multi-use conditions. Primary outcomes measured the maximum concentration of avobenzone in plasma from day 1 to day 21 of application. Secondary outcomes measured maximum plasma concentrations of the other 5 measured active ingredients in the same span of time.
A total of 48 individuals (50% women; mean age, 38.7 years) were randomized to 1 of 4 sunscreen groups; 44 participants completed the study. Sunscreen was applied at 2 mg/cm2 to approximately 75% of the body, or the area outside swimwear. During the 21-day application period, 34 blood samples were collected.
Maximum plasma concentrations of avobenzone from lotion, aerosol spray, nonaerosol spray, and pump spray were 7.1 ng/mL, 3.25 ng/mL, 3.5 ng/mL, and 3.3 ng/mL, respectively. Maximum plasma concentrations of oxybenzone for lotion and aerosol spray were 258.1 ng/mL and 180.1 ng/mL, respectively. Maximum plasma concentrations of octocrylene were 7.8 ng/mL for lotion, 6.6 ng/mL for aerosol spray, and 6.6 ng/mL for nonaerosol spray. Additionally, maximum plasma concentrations were 23.1 ng/mL (aerosol spray), 17.9 ng/mL (nonaerosol spray), and 13.9 ng/mL (pump spray) for homosalate and were 5.1 ng/mL (aerosol spray), 5.8 ng/mL (nonaerosol spray), and 4.6 ng/mL (pump spray) for octisalate. Maximum plasma concentrations of oxtinoxate were 7.9 ng/mL (nonaerosol spray) and 5.2 ng/mL (pump spray).
All 6 of the measured active ingredients had a geometric mean maximum plasma concentration >0.5 ng/mL, which was surpassed on day 1 of a single application of sunscreen. “This reinforces the need for additional research to determine the effect of systemic exposure of sunscreen ingredients,” the authors noted.
The investigators mentioned some limitations of the study, which included its indoor study setting, lack of study design to determine absorption difference by type and Fitzpatrick skin types, and variations in ingredients between products.
All 6 of the tested active ingredients “were systematically absorbed and had plasma concentrations that surpassed the FDA threshold for potentially waiving some of the additional safety studies for sunscreens,” the authors noted. “These findings do not indicate that individuals should refrain from the use of sunscreen.”
Matta MK, Florian J, Zusterzeel R, et al. Effect of sunscreen application on plasma concentration of sunscreen active ingredients: a randomized clinical trial. JAMA. 2020;323(3):256-267.