Stability of chemical UV filters in sunscreens exposed to vehicle cabin temperatures

Abstract

Background: Sunscreen companies recommend replacing your chemical sunscreen every year. Consumer inquiries about product integrity under excessive exposure to heat prompted the FDA to add a requirement statement to sunscreen products indicating a need to protect stored sunscreen from excessive heat and direct sun. If heat exposure indeed affects chemical sunscreen stability, then in some areas, replacement may be warranted earlier than a year. Methods: We examined real-life scenarios related to the storage of sunscreen containers inside vehicles sitting in natural sunlight to provide information about the stability of sunscreen active ingredients under real-life storage conditions. The active ingredients avobenzone, oxybenzone, homosalate, octinoxate, octisalate, and octocrylene in samples of sunscreens were examined after heat exposure over six months using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The calculated levels of each active ingredient were then compared between the non-heat exposed samples and the heat exposed samples using a paired t-test to look for decreases in active chemicals from heat exposure. Results: No important differences were seen for heat exposure in this study of 378 hours of temperatures above 37.8 °C, with an additional 292 hours of exposure to temperatures of 32.2-37.7 °C, and 3454 hours at 26.7-32.2 °C. Conclusions: This suggests such heat exposure does not result in degradation of the active ingredients of sunscreens with sun protection factors (SPF) of 30 and 50. This is important for individuals attempting to prevent sunburns and skin cancer.