Evidence exists on the systemic absorption of 4 sunscreen active ingredients; thus, additional studies must determine the systemic absorption of additional active ingredients and also the time required for systemic exposure to exceed 0.5 ng/mL as recommended by the US Food and Drug Administration (FDA).

The present study assessed 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, involving 48 healthy participants.

It randomized the participants equally to 1 of 4 sunscreen products formulated as a lotion, aerosol spray, nonaerosol spray and pump spray, and were directed to apply sunscreen product 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. The study obtained 34 blood samples over 21 days from each participant.

The study looked for the maximum plasma concentration of avobenzone over days 1 through 21, along with the maximum plasma concentrations of oxybenzone, octocrylene, homosalate, octisalate and octinoxate over days 1 through 21.

The study observed:

• Trial completion by 44 participants.
• The geometric mean maximum plasma concentrations of all 6 active ingredients were >0.5 ng/mL, and this threshold was surpassed on day 1 after a single application for all active ingredients.
• Avobenzone showed the overall maximum plasma concentrations of 7.1 ng/mL for lotion, 3.5 ng/mL for aerosol spray, 3.5 ng/mL for nonaerosol spray and 3.3 ng/mL for pump spray.
• Oxybenzone showed concentrations of 258.1 ng/mL for lotion and 180.1 ng/mL for aerosol spray.
• Octocrylene showed concentrations of 7.8 ng/mL for lotion, 6.6 ng/mL for aerosol spray and 6.6 ng/mL for nonaerosol spray.
• Homosalate showed concentrations of 23.1 ng/mL for aerosol spray, 17.9 ng/mL for nonaerosol spray and 13.9 ng/mL for pump spray.
• Octisalate showed concentrations of 5.1 ng/mL for aerosol spray, 5.8 ng/mL for nonaerosol spray and 4.6 ng/mL for pump spray.
• Octinoxate showed concentrations of 7.9 ng/mL for nonaerosol spray and 5.2 ng/mL for pump spray.
• Rash was the most common adverse event, occurring in 14 participants.

The study shows systemic absorption of all 6 of the tested active ingredients administered in 4 different sunscreen formulations. Additionally, their plasma concentrations surpassed the FDA threshold. However, these findings do not indicate that individuals should refrain from using sunscreen.

Source: 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):256-67.