Sunscreen Absorbed into the Blood, Consequences Unknown

By Kelly Young

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

Chemical sunscreen ingredients are systemically absorbed after one application, and some ingredients can stay in the blood for at least 3 weeks, according to an FDA study published in JAMA.

In a lab setting, 48 adults were randomized to receive one of four formulations of chemical sunscreens containing avobenzone, oxybenzone, octocrylene, homosalate, octisalate, or octinoxate. Sunscreen was applied once on the first day and four times on days 2 through 4. Participants had 34 blood samples collected over 21 days.

The maximum plasma concentration of avobenzone over days 1 through 21 — the primary outcome — was 7.1 ng/mL for lotion, 3.5 ng/mL for aerosol and nonaerosol spray, and 3.3 ng/mL for pump spray. For all six active ingredients, most participants had maximum plasma concentrations that were at or above the FDA's 0.5 ng/mL threshold (for possibly waiving additional safety studies) for as long as 23 hours after a single application. For homosalate and oxybenzone, over half of participants had above-threshold plasma levels 21 days after application.

The authors say their findings reinforce the need for further studies on sunscreen safety. Editorialists conclude: "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."