Ethylhexyl Methoxycinnamate
Ethylhexyl Methoxycinnamate (also known as Octinoxate or Octyl Methoxycinnamate) is the ester of 2-ethylhexyl alcohol and methoxycinnamic acid (CAS #5466-77-3). It is a clear, oil-soluble liquid and the most commonly used chemical sunscreen ingredient worldwide. It absorbs UVB radiation in the 280–320 nm range with peak protection at 310 nm, but provides no UVA protection. It is not highly photostable and can lose approximately 10% of its SPF efficacy within 35 minutes of sun exposure.
Provides effective UVB protection (280–320 nm, peak at 310 nm) and is cosmetically elegant due to its clear, lightweight, oil-soluble texture. It is permitted for use up to 10% in the EU and 7.5% in the US, and is considered safe as used in regulated sunscreen formulations. Photostability and broad-spectrum coverage are improved when combined with other sunscreen agents such as Tinosorb S.
Photostability is limited — loses ~10% SPF efficacy within 35 minutes; should always be combined with other sunscreen agents for broad-spectrum and stable protection. In vitro and animal studies suggest potential estrogen-like (hormonal) activity; while not confirmed under real-life human conditions, pregnant individuals and children under 2 years old are advised to opt for physical sunscreens (zinc oxide/titanium dioxide) or newer-generation Tinosorb-based alternatives as a precaution.
