UVA1 and the Rising Excitement of Mexoryl 400
AUTHOR: KARA HORACEK. AUGUST 2026.
We hear about UV rays a lot. But really, what are they? Why do we want to avoid overexposure, and what recent advances in the scientific community are trying to help you, the consumer, stay protected?
Ultraviolet rays are a form of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, spanning approximately 100–400 nm. The sun is the primary natural source, though artificial sources (tanning beds, welding arcs, germicidal lamps) also emit UV radiation. There are three divisions, known as bands, to separate types of UV rays. UVC is The shortest and most energetic UV wavelength. Spanning 100-280 nm, UVC is almost entirely absorbed by the ozone layer and atmosphere, so it does not reach Earth's surface under normal conditions. Artificially generated UVC is used for disinfection. UVB, spanning 280-315 nm, makes up for 5% of terrestrial UV radiation. This subdivision is the primary cause of sunburn and is a principal driver of vitamin D synthesis. The Sun Protection Factor, commonly SPF, on sunscreen labels primarily measures UVB protection. The final band is UVA. Encompassing wavelengths between 315 and 400 nm, it accounts for approximately 95% of UV radiation reaching Earth's surface and penetrates more deeply into the dermis than UVB. UVA is further subdivided into UVA2 (315–340 nm), shorter-wave UVA with some overlap in biological effects with UVB, and UVA1 (340–400 nm), longer-wave UVA responsible for photoaging, pigmentation changes, and oxidative DNA damage. UVA1 intensity remains relatively constant throughout the day and penetrates through clouds and window glass, unlike UVB. UVA-induced damage rarely presents definite or readily observable symptoms. It does not produce immediate sunburn, so patients often underestimate their cumulative exposure despite how both UVA and UVB contribute to skin cancer risk. Standard sunscreens block up to 98% of UVB, whereas their UVA protection is often far lower and harder to measure. Sunscreens are excellent at filtering UVB. For example, SPF 30 blocks ~ 97% of UVB rays, while SPF 50 filters ~ 98%. But, to lower skin cancer risk, preventing both UVA and UVB is necassary.
The recent innovation of Mexoryl 400 (MCE) stands apart from conventional UVA filters in one critical way: it targets the longest wavelengths of UVA1 with a peak absorption at 385 nm. Most existing UVA filters, like Avobenzone, leave a gap at the far end of the UVA spectrum. Mexoryl 400 is also photostable, unlike Avobenzone, which degrades under sunlight and requires photostabilizers to maintain efficacy. It’s creating quite the ripple within the dermatological community for a few reasons:
Live clinical trials demonstrated that sunscreens containing MCE at concentrations of 1–2% produced statistically significantly less UV-induced hyperpigmentation compared to reference sunscreens, as measured visually and using colorimetry.
The 380–400 nm range borders on visible light and has been implicated in conditions like solar urticaria, PMLE, lupus erythematosus, and dermatomyositis. Mexoryl 400 along with TriAsorB are both specifically highlighted as useful for these photosensitivity disorders.
Mexoryl 400 is part of a wave of next-generation filters alongside TriAsorB and bemotrizinol that represent a paradigm shift from "sunburn prevention" to comprehensive photoprotection across the full UV and near-visible spectrum.
As exciting as MCE is, as of July 2026, Mexoryl 400 is currently approved in Europe and other international markets but is not yet FDA-approved in the United States. The EU has 29 approved UV filters compared to only 16–17 in the U.S., and no new UV filter has been added to the U.S. monograph in over 25 years. In December 2025, the FDA issued a proposed order to add bemotrizinol as a GRASE filter, which may signal movement toward approving additional modern filters. If Mexoryl sounds interesting and like a product you wish to try, consumers in the U.S. can currently access Mexoryl 400 through European sunscreen products.
So, what does this mean for you? Do you need a new sunscreen? The American Academy of Dermatology recommends sunscreens with SPF 30 or greater and broad-spectrum UVA/UVB protection for all skin types. However, a recent study testing 38 different SPF 50/50+ sunscreens found minimal similarities in actual UVA protection levels, meaning not all "broad-spectrum" sunscreens are created equal. For consumers concerned about premature aging, hyperpigmentation, or photosensitive skin conditions, seeking out formulations containing this filter offers a meaningful upgrade in protection. If you think MCE sounds like something you’re interested in, talk to your dermatologist. We at Boutik Dermatology would be happy to speak with you about your health and how to best use your sunscreen.
