Mexoryl has been marketed as a breakthrough ingredient, providing protection that is said to be far more comprehensive than commonly used UVA filters such as Oxybenzone, Titanium Dioxide or Parsol 1789.
The ingredient has been licensed for use in Europe since 1993, where it is generically known as ecarnsule, and is incorporated into a number of leading sunscreen products.
Until now the FDA has refused to approve the ingredient and has not said why it will not approve it - a decision that many consider to be strange given that European legislation for cosmetic ingredients is generally considered to be tougher than in the US.
Although the drug has not been officially approved, L'Oreal, which is also the patent holder for Mexoryl, has been given the go ahead to market the daily moisturizer Anthelios SX with comprehensive sunscreen protection containing Mexoryl towards the end of 2006.
L'Oreal has marketed sunscreens using the ingredient in many countries across the world, and says it will be one of the first companies to start selling sunscreens including Mexoryl in the US following the FDA's approval of Mexoryl.
Although the vast majority of sunscreens now offer comprehensive protection against both UVA and UVB rays, scientific research regarding the dangers associated with UVA rays are becoming more compelling.
UVB rays commonly cause the skin to go red and burn. However, UVA rays penetrate the lower dermal layer of the skin, leading to wrinkling and a greater risk of developing skin cancer.
Because of this evidence UVA protection has become increasingly sophisticated in recent years, in an attempt to provide better sun protection.
With dermatologists having lauded Mexoryl's effectiveness at blocking UVA rays, some Americans have been forced to buy sunscreen products containing the ingredient over the internet and other foreign sources, in an effort to increase their protection from the sun.
Indeed many US pharmacists are said to have stocked sunscreens containing Mexoryl 'under the counter', charging between $30 and $50 a tube.
"It's an excellent UVA blocker with a decent track record in Europe and Canada ... I think this is an important addition to what we have available to us," said Dr Stephen Stone, president of the American Academy of Dermatology and professor of clinical medicine at Southern Illinois University School of Medicine.
Undoubtedly the fact that L'Oreal has been given the go-ahead to market a product containing the ingredient will bring about renewed calls for the FDA to approve the ingredient.