Homosalate
Homosalate is an oil-soluble chemical sunscreen agent that absorbs UVB radiation in the 295–315 nm range, with peak protection at 306 nm. It is not a strong UV filter on its own, providing only SPF 4.3 protection at its maximum allowed concentration of 10%, and it is not photostable, losing approximately 10% of its SPF protection within 45 minutes. Because it is a liquid, it is valued for its ability to dissolve other hard-to-solubilize powder sunscreen agents, such as Avobenzone, making it a useful formulation aid in sunscreen products.
Homosalate provides UVB protection and serves as an effective solubilizer for other sunscreen actives like Avobenzone, improving the overall formulation of broad-spectrum sunscreens. It must always be combined with other sunscreen agents to deliver adequate UV protection.
In vitro studies have indicated potential estrogenic activity, though these were not conducted on humans under real-world conditions. Long-term, full-body use should be approached with caution by those concerned about endocrine disruption. Regulatory limits vary by region: up to 10% in the EU and 15% in the US, with the EU considering a restriction to 1.4%. Not photostable — loses ~10% SPF protection within 45 minutes of UV exposure.
