Category: topical
Aliases: Parsol 1789, Butyl methoxydibenzoylmethane
Absorbs UVA (310–400 nm) via keto-enol tautomerisation. Photo-unstable alone — degrades ~40% in 1 hour of sun exposure. Stabilised by combination with octocrylene / Mexoryl / Tinosorb. Minimal systemic absorption (FDA 2019 study detected plasma levels but clinical significance unclear).