The questions surrounding sunscreen and labeling, which may have less to do with science and more to do with motivating human behavior, may prove to be the thorniest of all. Everyone agrees on the goal: Create a simple label that consumers can easily understand.

In addition to recommending the SPF limit on labels, FDA has proposed further label changes to help clarify the risks and benefits of sunscreen use and how to use the products properly. For example, FDA wants the label to avoid unsupported, misleading or confusing terms such as "sunblock," "waterproof," "all-day protection" and "visible and/or infrared light protection." And when the label says the product is "water resistant," or "very water resistant," it must mean that the product provides the stated SPF level after water resistance testing for a specified length of time. FDA and the industry also are wrestling with what it means to claim that a sunscreen is "broad-spectrum," that is, protective against both UVA and UVB.

Complexity is the problem because consumers want simplicity. Industry already has conducted studies that test the effectiveness of different ways to present information on the label. For example, Schering-Plough Health Care Products of Berkeley Heights, N.J., tested a label that contained another number in addition to the SPF to indicate the degree to which the product protected against UVA. "The second protection number created unnecessary complications and confusion for the consumer," says Patricia Agin, Ph.D., Schering-Plough's photobiology research director. "UVA should complement and not distract from SPF on the label. A descriptive approach better conveyed to consumers the added benefit of UVA protection and did not distract from the SPF number."

"SPF should remain the primary index of efficacy," agrees Jay Nash, Ph.D., of Proctor & Gamble Pharmaceuticals Inc., of Mason, Ohio, "and any additional descriptor should be independent and commensurate with this information. Simplicity is the key to public policy."

Simple or not, the labeling issue is not trivial because studies already show that consumers may not use sunscreens correctly. The public under-applies sunscreens by as much as half of the recommended amount, concluded a study published in the Archives of Dermatology. Consequently, the study argued, consumers are receiving only half of the SPF sunscreen protection they believe the product provides. Couple that with prolonged periods of baking in the sun and you have a recipe for future disease.

Larry Thompson is the editor of FDA Consumer.