There is only one sure and stable UVA filter: Mexoryl SX. Mexoryl sunscreens provide long-lasting, effective protection. The Mexoryl molecule is virtually impervious to sun exposure. In sun-protection research, Mexoryl SX has been patented by L'Oréal, and has been used in Ombrelle formulas since 1993. UVA rays are the main cause of Melanoma skin cancer. Only Mexoryl sunscreens block UVA rays. Using a Mexoryl sunscreen will help prevent skin cancer.