Mexoryl 400
Also known as: Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate, MCE
The first filter that protects against the long-UVA wavelengths linked to daily aging and pigmentation — and currently only L'Oréal has it.
What It Does
Deep Dive
Mexoryl 400 is L'Oréal's newest UV filter, patented in 2018 and launched commercially in 2022. It fills a specific gap: traditional UVA filters (including avobenzone and Mexoryl SX) start losing effectiveness above 370 nm, but long-UVA wavelengths (380–400 nm) make up about 30% of daily UV exposure and are increasingly linked to pigmentation, melasma, and photoaging. Mexoryl 400 is the first filter to target that window specifically. You'll find it in La Roche-Posay Anthelios UVMune 400, Vichy Capital Soleil, and Skinceuticals Advanced Brightening. It's not FDA-approved (see: frozen 1999 monograph), so US users need to import. If you have melasma, hyperpigmentation, or reactive skin that flares in daylight even through regular SPF, this is the filter to seek out.