Sunscreen season is fully upon us, which means that most of us have been rifling through our beach bags and bathroom cabinets to see what we have left over from last year and scouring the store shelves to try to figure out what brands to try out this year. Which sunscreen is the safest and most effective?

It turns out that some of the best sunscreens may not even be available — yet — in stores here in the U.S. That's because there are a slew of sunscreen ingredients that have not yet been approved by the U.S. Food and Drug Administration (FDA) for use in sunscreens. But those same ingredients have been in use in Europe for years. And they may be more effective — and safer — than those used in the products we currently have available.

There are a number of ingredients in question, namely two called Mexoryl SX and Mexoryl SL, developed by the French company LaRoche-Posay Laboratoire Dermatologique, and two more called Tinosorb S and Tinosorb M, developed by the German chemical giant BASF. According to the Environmental Working Group (the non-profit agency that ranks sunscreens, cosmetics and personal care products based on toxicity,) these are promising UVA filters that may be more stable and more effective than the chemicals currently used in U.S. sunscreens.

So where are these wonder-chemicals and why won't you find them on store shelves? Despite the fact that these chemicals and several others have been widely used in Europe for the last 10 years, with numerous studies citing their efficacy and safety, they have not managed to attain approval from the FDA to be used in U.S. markets. Last fall, in a bipartisan effort to speed up this bureaucratic process, Congress passed the Sunscreen Innovation Act which required that the FDA work through its backlog of applications and streamline its existing review process. The FDA has not updated its list of approved sunscreen ingredients since 2009.

Congress hoped that the move would force the FDA to approve some of the applications stagnating in its offices and allow products containing these chemicals to hit American markets. But they were wrong. The FDA recently rejected all eight applications for new sunscreen ingredients that it had pending. In a statement released to the Boston-based website, BostInno, an FDA spokeswoman explained the decision:

"While the SIA [Sunscreen Innovation Act] includes strict deadlines for FDA to take action on sunscreen ingredients, it does not relax FDA’s scientific standards for evaluating an ingredient’s safety and effectiveness. At this time, there is not enough data to determine that any of the ingredients under review are generally recognized as safe and effective."

Theresa Michele, director of the FDA's Division of Nonprescription Drug Product, further explained the agency's decision in a blog post entitled "Shedding some light on FDA's review of sunscreen ingredients and the Sunscreen Innovation Act."

"While information on marketing history in other countries is helpful, what we can learn from it is limited. For example, such information doesn’t tell us anything about the long-term effects from use of the ingredient or how much is absorbed. Because of the widespread daily use of sunscreen products by a broad population, including babies and pregnant women, FDA has proposed data requirements that will allow us to determine that sunscreen ingredients are generally recognized as safe and effective."

So there you have it. At the moment, for better or for worse, those ingredients are not available to American consumers. And though that could change in the next few months or years, you can bet that it won't change in time for you to stock up on sunscreen this summer. For tips on what you can and should look for when choosing sunscreen this year, check out this FDA video on the meanings behind sunscreen labels:

Does anyone else find it ironic that the branch of the FDA tasked with regulating sunscreen seems to be overprotective in the chemicals it approves, while the branch that regulates personal care products and cosmetics has seemingly no control over the ingredients used in the products Americans slather on their bodies every day?

Related on MNN:

Why Europe has better sunscreens than we do
Ingredients that have been used in Europe for years are still awaiting approval for use in the U.S.