Why doesn’t Typology use isoamyl p-methoxycinnamate (amiloxate)?

Amiloxate is an ester formed by reacting methoxycinnamic acid with 2-ethylhexanol, with the molecular formula C18H26O3. Its structure features a branched alkyl chain and an aromatic ring substituted with a methoxy group (-OCH₃), granting the molecule selective UV absorption properties. Isoamyl p-methoxycinnamate is combined with other filters, such as titanium dioxide or oxybenzone, to broaden its protection spectrum. In Europe, the maximum allowed concentration of amiloxate in sun care products is regulated at 10%, according to Annex VI of Regulation (EC) No. 1223/2009 on personal care products. In other regions of the world, such as the United States or Asia, these regulations vary.

In the European Union, Australia, China, India, and South Africa, amiloxate may be used at a maximum concentration of 10%, whereas this filter is not approved in the United States, Canada, or Japan.

Amiloxate is recognized for its ability to protect hair and skin from the sun’s harmful rays. However, it is criticized for the following reasons:

What is the health impact of isoamyl p-methoxycinnamate?

Several studies in vitro have shown the potential cytotoxicity of isoamyl p-methoxycinnamate. In human hepatic cell models (SMMC-7721), exposure to amiloxate results in a significant decrease in cell viability and inhibition of proliferation. This decline coincides with a marked increase in reactive oxygen species, reduced mitochondrial membrane potential, and activation of mitochondrial apoptosis pathways involving Bax, Bcl-2, and Caspase-3. Isoamyl p-methoxycinnamate also disrupts intracellular redox balance by inhibiting antioxidant enzymes such as catalase, glutathione peroxidase, and superoxide dismutase, while increasing oxidative stress markers such as malondialdehyde and lactate dehydrogenase.

Furthermore, studies in animal and cellular models indicate that isoamyl p-methoxycinnamate may disrupt the endocrine system. This filter has shown a antiestrogenic and antiandrogenic activity in tests in vitro using yeast expressing human estrogen receptors (ERα) and androgen receptors. Studies in rats with octinoxate, a sunscreen filter structurally similar to amiloxate, showed interference with the hypothalamic-pituitary-thyroid axis. Although data on isoamyl p-methoxycinnamate are limited, its structural similarity to octinoxate raises concern.

Finally, isoamyl p-methoxycinnamate is recognized as a potential photoallergen. Although cases are rare, several photopatch test studies have reported allergic or photoallergic reactions linked to amiloxate. In a study of 111 patients with a positive reaction, two photoallergy cases to this sunscreen filter were recorded, a reaction rate of 1.8%. Despite the low rate, this shows a not negligible photoallergic risk of isoamyl p-methoxycinnamate.

What is the environmental impact of isoamyl p-methoxycinnamate?

The chemical UV filters, including isoamyl p-methoxycinnamate, do not remain confined to the skin surface. Once rinsed off during swimming or showering, they enter aquatic environments. Several studies and policy initiatives highlight ecological effects of this contamination, especially in marine settings. One of the most concerning impacts affects coral reefs. Observations have revealed a bleaching of corals on contact with certain UV filters, including isoamyl p-methoxycinnamate. This phenomenon, which indicates extreme cellular stress in corals, compromises their survival and weakens the marine ecosystem. In response, the state of Hawaii has introduced legislation to restrict sunscreens containing UV filters deemed harmful to ocean health, including oxybenzone and amiloxate.

The Palau government also took a stance. In 2018, it enacted a law banning the use and sale of sunscreens containing ten chemical substances, including isoamyl-p-methoxycinnamate. This regulation includes financial penalties: retailers that violate it face a $1,000 fine. This measure reflects a clear objective to protect aquatic environments. Faced with these alerts, the French Agency for the Safety of Health Products (AFSSAPS) adopted a more nuanced position. It does not endorse or reject isoamyl-p-methoxycinnamate use and monitors emerging data.