Why doesn’t our formula use octisalate?

Octyl salicylate is a common filter in sunscreens, yet its tolerance profile faces growing criticism. Here are the main concerns against it:

Ethylhexyl salicylate, an irritating sunscreen filter?

Dermatologically, octisalate is a UV filter considered well tolerated, with a low allergenic potential. A 2012 reference study by the European Multicentre Photopatch Test Study evaluated skin reactivity to various UV filters in a large panel of participants. This study, which involved 1,031 volunteers, recorded 2 reactions to ethylhexyl salicylate, representing a reaction rate of 0.19%. Observed symptoms were localized redness without systemic reactions. Octisalate is not known as a photoallergen, meaning that after application and UV exposure, allergic reactions are rare.

Can octisalate penetrate the skin barrier?

The question of skin absorption and systemic distribution of octyl salicylate is gaining interest in discussions on potential endocrine effects of some organic filters. In a study with six volunteers, the penetration of ethylhexyl salicylate was assessed using the tape-stripping method, which allows one to analyze the compound concentration at different depths of the stratum corneum. Two types of formulations were tested: an oil-in-water emulsion gel and a petroleum jelly base.

• With the emulsion formulation, approximately 25.6% of the applied dose was found in the stratum corneum.

• With petroleum jelly, this proportion dropped to 11%.

The authors observed that the concentration in the superficial stratum corneum was higher with the emulsion than with the gel. The concentration in deeper layers remained moderate but exceeded that of the gel. These results show that formulation affects the penetration of octyl salicylate without supporting significant systemic absorption.

Another study evaluated the systemic absorption of sunscreen formulations containing multiple chemical filters, including 5% ethylhexyl salicylate. The product was applied in a generous layer to the entire forearms of nine volunteers without occlusion. It was removed after 12 hours. Urinary analysis up to 48 hours after application estimated that 1 to 2% of the total formulation had been absorbed. The study did not specify the proportion of each UV filter in the formula (avobenzone, octocrylene, octisalate, and ethylhexyl methoxycinnamate). This prevents determining the share attributable to octyl salicylate.

Is ethylhexyl salicylate an endocrine disruptor?

Octisalate is suspected of disrupting the endocrine system and interacting with hormone receptors, including estrogen receptors. In the case of ethylhexyl salicylate, several scientists assessed this risk with reassuring results. A study using predictive modeling evaluated the theoretical affinity of ethylhexyl salicylate for the estrogen receptor (ER). Following this computational approach, octisalate was classified as a compound that does not bind to the estrogen receptor.

These results were confirmed by an experimental bioassay using a recombinant yeast system expressing ERα. This method, based on β-galactosidase induction in the presence of an estrogenic ligand, showed that ethylhexyl salicylate produced a flatter dose–response curve than estradiol. Its relative estrogenic potency was estimated at 1/2,000,000 that of estradiol, indicating negligible biological activity.

These data appear to indicate that octisalate does not exert an estrogenic effect.

Does octisalate pose a risk to the environment?

Like other organic sunscreen filters, ethylhexyl salicylate can affect the environment when released through swimming. Its lipophilic structure, designed to resist water, drives its persistence in aquatic systems. Moreover, studies show octisalate can accumulate in living organisms, in tissues rich in lipids. Research on zebrafish (Danio rerio) embryos indicates that exposure to ethylhexyl salicylate during embryonic development can cause cardiovascular malformations, abnormal lipid accumulation, and impaired tissue oxygenation. These outcomes stem from altered expression of genes involved in lipid metabolism and vascular development.

Although these results cannot be extrapolated to humans, they underscore octisalate’s disruptive potential on aquatic ecosystems.

Although studies are ongoing, ethylhexyl salicylate is suspected of contributing to coral reef degradation, similar to other organic UV filters, such as octocrylene. Recent metabolomic profiling studies on the coral Pocillopora damicornis have shown that ethylhexyl salicylate increased stress in this marine organism. At a concentration of 50 µg/L, this sunscreen filter triggered increased production of a steroid naturally present in corals, (3β,5α,8α)-5,8-epidioxy-ergosta-6,24(28)-diene-3-ol, considered an environmental stress marker. When concentration reached 300 µg/L, a stronger response appeared, characterized by significant increases in polyunsaturated fatty acids, lysophosphatidylcholines, and lysophosphatidylethanolamines, molecules linked to inflammatory responses and oxidative stress. These data suggest that octisalate exposure can disrupt coral metabolism.