Why doesn't Typology use Octocrylene?

Even though octocrylene is a permitted and regulated sunscreen filter in the European Union and the United States, it does not imply that it is entirely harmless.

What are the risks of octocrylene to skin and human health?

• Octocrylene is linked to risks of photoallergies.

  Octocrylene is generally well tolerated by the skin. A German study conducted on 2,577 patients subjected to a patch test with a 10% octocrylene solution revealed only two mildly positive reactions, a rate of just 0.08%. These results were confirmed on a European scale: another multicentre study noted an allergic reaction rate of 0.7% in over 1,000 patients suspected of contact dermatitis related to sun care products. The children however, appear to be slightly more sensitive than adults, likely due to the fragility of their skin barrier and the increased prevalence of atopic dermatitis in this age group.

  Photoallergic reactions are more common. In a large European photopatch test study, about 4% of the people tested showed a photoallergic reaction to octocrylene. This type of reaction seems strongly linked to a prior sensitisation to topical ketoprofen, an anti-inflammatory with a similar chemical structure. In an Italian study involving 156 patients, 61.5% of octocrylene photoallergy cases were associated with a concurrent reaction to ketoprofen. Several hypotheses have been put forward to explain this co-reactivity, including a possible degradation of octocrylene into benzophenone, a photoreactive compound.

A study conducted in 2021 assessed the formation of benzophenone in sun protection products tested at purchase and then after accelerated ageing simulating a year of storage. Benzophenone was detected in all products initially containing octocrylene, but not in the one that was devoid of it. The average rates doubled after ageing (from 39 to 75 mg/kg), reaching up to 435 mg/kg.

The authors of the study thus concluded:"Our work unequivocally establishes that octocrylene undergoes a slow retro-aldol condensation reaction which results in the formation of benzophenone. This process occurred in all tested commercial sunscreens containing octocrylene, leading to a concurrent increase in benzophenone concentration as the product ages".

• Octocrylene is suspected to be an endocrine disruptor.

  There are also suspicions about the impact of octocrylene on the endocrine system. Some studies in rats have shown that octocrylene can affect the metabolism of thyroid hormones. In a study conducted in 2019, high exposure (up to 193 mg/kg/day) led to an increase in the enzymes responsible for the degradation of thyroxine (T4), resulting in compensatory stimulation of the thyroid via the hypothalamic-pituitary-thyroid axis. However, this reaction is considered to be specific to rodents. Humans have a T4 binding protein in the blood, which limits the depletion of this hormone and therefore reduces the risk of comparable thyroid stimulation. For this reason, the Scientific Committee for Consumer Safety (SCCS) does not include these effects in its assessment of human risks, although vigilance remains necessary.

  However, if octocrylene is accused of being an endocrine disruptor, it is also due to its transformation into benzophenone. Indeed, several studies have reported oestrogenic-like activity in vitro on cells and in vivo on rats/zebrafish due to benzophenone. This compound could have an acute effect on endogenous reproductive hormone levels in humans and interfere with the functioning of the endocrine system (hypothalamic-pituitary-gonadal axis), potentially affecting human health after topical application. Given that octocrylene has a high risk of transforming into benzophenone, concerns remain.

• Octocrylene could potentially be carcinogenic.

  For the same reasons, that is to say, by degrading into benzophenone, octocrylene could present a carcinogenic risk. A 2008 report revealed that exposing human lung cancer cells to non-toxic concentrations of benzophenone could confer a behavioural change in the cells towards mesenchymal phenotypes (epithelial-mesenchymal transition). This is a process which facilitates the formation of metastases, that is, the ability of anoikis-resistant tumour cells to migrate and invade surrounding tissues to form secondary tumours. Other studies have reportedly identified effects of this compound on mammary tumorigenesis in mice.

  However, whether it's benzophenone or octocrylene, more studies are needed to make a definitive statement. Furthermore, the CSSC concluded in its latest report that octocrylene does not pose a carcinogenic risk.

Are there environmental risks associated with Octocrylene?

Finally, beyond the risks posed by octocrylene to human health, this UV filter raises concerns regarding its impact on aquatic ecosystems, particularly coral reefs. Studies conducted on the coral Pocillopora damicornis have shown that exposure to concentrations of 300 μg/L and above resulted in a massive closure of corals. Even more concerning, researchers have highlighted an accumulation of octocrylene and its derivatives in coral tissues, from 5 μg/L — levels comparable to those measured in some coastal areas. These derivatives, formed by coupling octocrylene with fatty acids, are very lipophilic and likely to accumulate over time. Furthermore, traces of octocrylene and its metabolites have been detected in various marine organisms, such as dolphins and mussels, suggesting a fairly broad bioaccumulation.

In light of these findings, some regions, such as Hawaii, have banned the sale of products containing octocrylene to protect coral reefs.