INTRODUCTION
Ultraviolet (UV) radiation from sunlight contributes to skin damage, premature aging, and the development of skin cancer.1,2 UV rays, both UVA and UVB, penetrate the skin and cause both direct and indirect damage to skin cells. UVB (280-320 nm) affects mostly the epidermis and is the primary cause of erythema.3 UVA (320-400 nm), instead, penetrates deeper into the dermis and is the main culprit in photoaging.4 The damage from UV radiation leads to mutations that can disrupt normal cell growth and repair processes, increasing the risk of skin cancers.5 Prolonged exposure to UV radiation also accelerates the breakdown of collagen and elastin,6,7 leading to premature skin aging, sunburns, and weakened immune responses.
When used properly, sunscreen is effective in preventing sunburn, skin cancer, and premature photoaging. Sunscreens are generally categorized into 2 types: physical and organic, based on the composition of their UV filters. Physical sunscreens contain UV filters such as zinc oxide and/or titanium dioxide, while organic sunscreens are formulated with chemical UV filters. Some of the most commonly used chemical UV filters include avobenzone, octocrylene, homosalate, and octisalate. Contrary to popular belief, both physical and chemical filters function by absorbing, reflecting, and scattering UV radiation.8
In 2019 and 2020, studies conducted by the US Food and Drug Administration (FDA) revealed systemic absorption of chemical UV filters when sunscreen was applied at the maximal usage levels.9,10 These findings led the FDA to request further safety data on sunscreens containing chemical UV filters.
While this data is still being gathered, we conducted a retrospective analysis of approximately 39,000 subjects who participated in clinical safety studies examining sunscreens formulated with the 4 most commonly used chemical UV filters: avobenzone, octocrylene, homosalate, and octisalate. The results of this analysis provide valuable insights into the safety profile of these chemical UV filters, contributing to the ongoing effort to ensure the efficacy and safety of organic sunscreens.
