Abundant research exists showing the need to protect skin from the sun's UVA rays (Sources: Photochemistry and Photobiology Science, August 2004, pages 736-740 and Cutis, September 2003, pages 11-15). The only three ingredients approved by the FDA that can protect skin from UVA damage are avobenzone, titanium dioxide, and zinc oxide.* (Outside of the US, Tinosorb and Mexoryl SX are also UVA-protecting ingredients.) It is critical that one of these ingredients appear in the active ingredient list of any sunscreen (Sources: Journal of the American Academy of Dermatology, December 2000, pages 1024-1035; Photodermatology, Photoimmunology, and Photomedicine, December 2000, pages 250-255; British Journal of Dermatology, August 1999, pages 250-258.)

Despite the research showing these ingredients as fundamental to a sunscreen's ability to protect skin, nagging questions about avobenzone's stability persist. This uncertainty resulted from a story that appeared in Health magazine (May/June 1998) reporting on research conducted by Robert Sayre, a physicist in photobiology at the University of Memphis, suggesting that avobenzone may break down in as little as 30 minutes when exposed to sunlight.

Sayre's study, which was never published or peer reviewed, (Source: Cosmetics & Toiletries, November 1999, pages 84-90) caused a commotion in the cosmetics industry. If Sayre was right (he wasn't, but I'll get into that in a second), a lot of sunscreen products should have been thrown in the garbage. Unfortunately, Health magazine did not look into how Sayre came up with his findings; his work was done only in a petri dish and not on human skin and he used far less than the amount required by the FDA for sunscreen testing. Even more significantly, there are still no other studies substantiating Sayre's results anywhere in the cosmetics or medical world.

It is critical for consumers to know that avobenzone is not some untested or untried sunscreen agent. It has been around since 1981 and is one of the most widely used sunscreen ingredients in the world. It is also the No. 1 sunscreen agent in Canadian, Australian, and European sunscreen formulations. The FDA approved avobenzone's use as a sunscreen agent in the United States after more than seven years of study. Avobenzone had to meet scrupulous performance standards when Hoffman LaRoche applied for it to receive new drug status from the FDA. New drug status is the most stringent FDA classification and requires more safety studies and efficacy substantiation than you can imagine. Avobenzone held up under all of the FDA's safety and potency protocol, or it wouldn't have been approved (www.fda.gov, Federal Register 1999: 64: 27666-27963.)

Even more significant, the January 1996 issue of Journal of Chromatography BioMedical Applications contained a study that looked at the issue of sunscreens degrading when exposed to sunlight. Their conclusion for avobenzone was as follows: "After 72 hours Parsol 1789 [avobenzone] in the sample exposed to the sun was decreased by up to 25% of the initial concentration." That 25% decrease was after 72 hours (far longer than anyone is supposed to rely on a sunscreen) and is a far cry from the 50% decrease reported by Sayre after only 30 minutes.

The definitive answer to the question about whether or not avobenzone is a stable sunscreen ingredient is that it is absolutely stable and there is substantial research showing that to be the case. (Sources: Journal of Investigative Dermatology, October 2003, pages 869-875; Journal of Cosmetic Science, November/December 2003, 589-598; Photodermatology, Photoimmunology, and Photomedicine, August 2003, pages 190-194 and August, 2000, pages 147-155; Photochemistry and Photobiology, February 2002, pages 122-125; Internet Photochemistry and Photobiology, www.photobiology.com/photobiology99/contrib/finlay/; and The Journal of Investigative Dermatology, August 2001, pages 256-267).

Avobenzone has value because it is one of only three active sunscreen ingredients available in the United States that protect skin from the entire UVA spectrum (the other two are titanium dioxide and zinc oxide). Without avobenzone, U.S. sunscreen options would be narrow indeed, and unless you have a known allergy to it, there is absolutely no reason to avoid avobenzone when shopping for effective, broad-spectrum sunscreens.

*Avobenzone may appear on labels as butyl methoxydibenzoylmethane