"I've always heard the higher the SPF (sun protection factor) the better, until you get to SPF 45," said Lim, who finally bought whatever happened to be in front of her. "Now my husband says the SPF doesn't matter as much as how much you use. What's the right amount? Do I have to apply it under their clothes? And how bad of a mother am I if I forget to reapply it?"
Critics of the agency say the lack of formal regulations has spawned misleading claims on products and put consumers at risk by encouraging them to rely too heavily on sunscreen for protection.
The FDA expects to finalize the rules in October; they would take effect by 2012.
In the meantime, to help consumers make decisions — and light a fire under the FDA — the Environmental Working Group on Monday released its annual Sunscreen Safety Guide, which rates sunscreens, lip balms and moisturizers, and features a database searchable by brand name. On Tuesday, Consumer Reports will issue its sunscreen guide.
The EWG, an advocacy group that has waged a four-year campaign promoting strict sun-safety standards, slammed the majority of the 1,400 products it tested. It recommends only 39 of 500 beach and sport sunscreens, primarily because of what it called "a surge in exaggerated SPF claims above 50" and concerns about ingredients in the products.
"Hats, clothing and shade are still the only completely reliable sun protection," said Jane Houlihan, EWG's vice president for research.
In fact, the long-delayed FDA rules would update labels to stress the importance of a comprehensive approach to sun protection that encourages seeking shade and covering up.
Sunscreen can help protect against sunburn, but contrary to what many people think, it hasn't yet been shown to prevent skin cancer or premature skin aging, according to the FDA.
Research has found that people who use sunscreen tend to stay in the sun longer than they might otherwise. That is particularly true if a product has a high SPF number, ratings the Environmental Working Group says "sell a false sense of security."
The group reported a 33 percent increase from last year in the number of products labeled with an SPF higher than 50. But the new federal guidelines would cap SPF claims at 50+ because there's little evidence that higher SPF products offer more protection.
SPF numbers, a familiar but baffling system for consumers, primarily measure protection from the UVB (ultraviolet light with a shorter wavelength) rays that cause sunburn.
A product labeled SPF 15 blocks about 93 percent of the sun's UVB rays; an SPF 50 protects against about 98 percent, said Dr. Henry Lim, chairman of the department of dermatology at Henry Ford Hospital in Detroit.
Because 100 percent blockage isn't possible, products labeled SPF 70 or 100 don't make much sense, said Lim.
"Rather than increasing SPF factor, the push now is to make a sunscreen product cover both UVA and UVB — how to make it broader," he said.
UVA (ultraviolet light with a longer wavelength) radiation facilitates tanning but also can damage the DNA of cells deep within the skin, contributing to skin cancer and premature aging.
Though many products are labeled "broad spectrum," consumers can't currently tell how much protection a sunscreen provides against UVA rays. The Environmental Working Group reported it found that one popular children's sunscreen marketed as SPF 100 had a UVA protection factor of 9, which is lower that you might expect.
Under the proposed guidelines, labeling would be expanded to include a four-star system that tells consumers how well the product protects against UVA rays.