Homosalate (6.50%)
Homosalate (CAS #118-56-9) 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 a liquid at room temperature, which makes it useful for dissolving other hard-to-solubilize powder sunscreen agents such as Avobenzone. On its own it provides only modest SPF protection (approximately SPF 4.3 at its maximum allowed concentration of 10%) and is not photostable, losing around 10% of its SPF protection within 45 minutes.
Homosalate provides UVB protection and serves as a solubilizing vehicle for other sunscreen actives such as Avobenzone, enabling more stable and effective broad-spectrum sunscreen formulations when combined with complementary filters.
In vitro studies have indicated potential estrogenic (endocrine-disrupting) activity; while these were not conducted under real-world human conditions, caution is advised for long-term, full-body use. The EU is considering restricting its use to 1.4% (down from the current 10% EU / 15% US limits) due to safety concerns. Not photostable on its own and must be combined with other sunscreen agents for adequate protection.
