Mexoryl 400: The Filter Built for the UVA Rays Everyone Ignored
Ultra-long UVA1 is the final frontier of photoprotection.
Mexoryl 400 (MCE) was approved in the EU in 2019 and absorbs in the ultra-long UVA1 range around 370-400 nm, peaking near 385 nm — wavelengths most older filters miss.
Dermatologists highlight Mexoryl 400 because it reaches deep into the ultra-long UVA1 range near 385 nm, closing a gap older filters leave open and helping with UVA-driven pigmentation.
Questions we get a lot
What is Mexoryl 400 and why does it matter?
Mexoryl 400 (MCE) is a newer UV filter approved in the EU in 2019 that absorbs ultra-long UVA1 light around 370-400 nm, peaking near 385 nm. These long wavelengths penetrate deeply and drive pigmentation and aging, and most earlier filters cover them poorly — which is why Mexoryl 400 is seen as filling a real gap.
Why is ultra-long UVA1 protection important?
Ultra-long UVA1 (around 370-400 nm) penetrates deeper into skin than other UV and contributes to free-radical damage, premature aging and pigmentation, including melasma. Because many conventional filters drop off in this range, a filter like Mexoryl 400 that targets it improves real-world broad-spectrum coverage.
Which sunscreen filters are approved in the US vs the EU?
The EU has approved 34 UV filters for sunscreens; the US allows about 16 (now 17 with bemotrizinol's 2026 approval). Filters widely used in Europe and Asia — such as bisoctrizole, drometrizole trisiloxane and Mexoryl 400 — remain under FDA review, which is why US options have lagged.
r/SkincareScience: 'Why is Mexoryl 400 such a big deal for UVA protection?'