A recent clinical trial has revealed that several active ingredients in sunscreen are detected at high levels within the blood after only one day of frequent use.
Sunscreen products are routinely recommended and utilised for prevention of skin damage. In spite of their widespread use, comparatively little is understood about the impact of systemic exposure to the common active constituents within sunscreen preparations on human health.
The US Food and Drug Administration (FDA) guidelines for sunscreen formulations dictate that blood quantities of sunscreen ingredients in excess of 0.5ng/mL may pose safety concerns. In this instance, non-clinical toxicology studies (i.e. systemic carcinogenicity and further developmental and reproductive assessment) are warranted to determine suitability.
This particular clinical trial included 24 healthy participants who were randomised to receive topical application of one of four commercially available sunscreen products. The formulations were applied to 75% of body surface area in 2mg amounts, four times daily in accordance with label instructions, over four consecutive days. Researchers evaluated the overall exposure of specific ingredients (avobenzone, oxybenzone, octocrylene and ecamsule) present in the sunscreens by way of multiple blood samples collected over a seven-day period.
Liquid chromatography was used to assess the plasma concentrations of each of the specified ingredients. All four constituents analysed exceeded 0.5ng/mL. Considering the lack of knowledge on the clinical effects of exposure above 0.5ng/mL, in addition to the safety parameters set by the FDA, further research is justified.
The four ingredients measured were specifically selected because they are frequently used in the manufacture of over-the-counter sunscreen preparations. Of particular interest in this study was avobenzone, one of the most prevalent UVA filters utilised in sunscreen formulas. This is the first clinical trial to capture exposure data for this compound.
While this research does not suggest any immediate risks to human health associated with the use of sunscreen, it does highlight a requirement for further investigation. The 0.5ng/mL threshold established by the FDA is centred on the theory that this is the maximum level below which the carcinogenic risk of any unfamiliar compound is considered low enough to negate the need for additional toxicology assessment. Beyond this limit, assumptions of safety are unfounded.
Given the uncertainty of the significance of the study’s findings, for the time being, it is advised that individuals continue to use sunscreen.
- Matta MK, Zusterzeel R, Pilli NR, et al. Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients: A randomized clinical trial. JAMA 2019 May 6, [Abstract]