Mexoryl sunscreen was originally formulated and patented for La Roche Posay's Anthelios sunscreen. Many sunscreens on the market only deliver UVB protection. Mexoryl sunscreen, as a chemical UV filter, was created to specifically keep the skin safe from exposure to UVA rays and with the intention of providing broad spectrum protection (protection from both UVA and UVB rays) when combined with other sunscreens in different formulas. Also, many chemical sunscreens are not photostable and Mexoryl sunscreen aims to provide that photostability, even when combining with these very same non-photostable sunscreens in various products.
The patent for Mexoryl is owned by L'oreal, as the parent company of La Roche Posay, and appears to be used in a number of different sunscreens today, including:
When combined with other sun filtering agents such as titanium dioxide, avobenzone (Parsol 1789), octocrylene or Tinosorb S, for example, Mexoryl sunscreen is able to advance its protection to cover a broad spectrum with protection against both UVA and UVB rays. eg. Anthelios SX contains avobenzone for long UVA protection and Octocrylene for UVB protection, in addition to Mexoryl, which covers the short UVA protection. So the combination of the 3 filters covers the complete broad spectrum.
Avobenzone, or otherwise known as Butyl Methoxydibenzoylethane, is known to break down into potentially harmful ingredients when exposed to the sun, thereby reducing its UVA protection efficacy.
Octocrylene on the other hand, produces free radicals when exposed to sunlight, damaging the DNA and potentially causing cancer.
Another sunscreen combined with Mexoryl sunscreen in two of the Anthelios' sunscreens is Tinosorb S. These are Anthelios Dermo Pediatrics Lotion 45 and Anthelios Spray SPF 45. Tinosorb S is a stable chemical sun filter that blocks both the UVA and UVB rays and also helps to increase the stability and effectiveness of other chemical sun filters.
Mexoryl SX and Mexoryl XL are photostable UVA absorbers. Effectively this means they don't degrade in sunlight. Some claims are for 24 hours after initial application. This contrasts with avobenzone, a known non-photostable sunscreen that must be combined with stabilizers to prevent it breaking down in sunlight. Without photostability, the sunscreen decreases in efficiency and reapplication is required often.