Q: I went to buy sunscreen. I spend a lot of time in the pool and wanted to buy a sunscreen that was waterproof. I couldn't find any. Have the labels changed?
A: Most sunscreen products have new labels. Mandated by the U.S. Food and Drug Administration (FDA), the new rules should provide more useful information with fewer misleading terms. The changes are good ones for consumers.
The FDA has also banned the term "sunblock." Instead, look for labels that state, "broad spectrum." A broad spectrum sunscreen must pass tests proving that it truly protects against both ultraviolet A (UVA) and ultraviolet B (UVB) rays.
When sunlight hits your skin, it's being exposed to UVA and UVB rays. UVB rays are the main cause of sunburn, while UVA rays can prematurely age and wrinkle skin. Both contribute to skin cancer. That's why you always want a broad spectrum product.
Sunscreens vary in their ability to protect against UVA and UVB based on their SPF, or sun protection factor. SPF is a measurement of how much longer it takes for your skin to turn red from the sun after applying the sunscreen. Say your skin turns red after 10 minutes in the sun. Sunscreen with an SPF of 15 would prevent your skin from turning red for 150 minutes under the same conditions.
You might think that an SPF of 30 would work twice as well as an SPF of 15, but that's not necessarily the case. While SPF 15 filters out approximately 93 percent of all incoming UVB rays, SPF 30 filters out 97 percent and SPF 50 boosts that to 98 percent.
The American Academy of Dermatology recommends using a sunscreen with an SPF of at least 30. According to the FDA, you don't need a sunscreen with an SPF higher than 50. The FDA says there's no evidence that sunscreens with an SPF above 50 offer any additional protection.
(Howard LeWine, M.D., is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)
(For additional consumer health information, please visit http://www.health.harvard.edu.)