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Our tests of 20 sunscreens and three moisturizers with sunscreen showed that you can't always rely on the SPF number, a measure of protection from burning ultraviolet B (UVB) radiation, which causes sunburn and contributes to skin cancer. We also tested for protection against ultraviolet A (UVA) rays, which tan and age skin, and also contribute to skin cancer. We found seven sunscreens that did well enough against both UVA and UVB to recommend.
Alas, there are no trips to Tahiti for our sunscreen panelists--they go to a lab. In UVB tests, sunscreen is applied to a rectangular area of panelists' backs. They soak in a tub of water and then six spots are exposed for set times to UVB radiation from a sun simulator. About a day later, the six spots are examined for redness. The resulting UVB Ratings reflect each product's actual effectiveness, not how close it came to meeting its SPF claim. To test for UVA protection, we follow the same process using a different group of panelists but we use UVA rays and check for tanning instead of redness.
In addition, we use a test based on the Food and Drug Administration's "critical wavelength" test, required for sunscreens that claim broad-spectrum protection. It assesses how well UV rays are absorbed by clear plastic plates treated with sunscreen. Two products came in slightly below the critical wavelength threshold in our tests. (Results can vary depending on the nature of the plates used.) The critical wavelength results are not used in the UVA ratings.
Overall scores are based on results of the above UVB and UVA tests.
For the moisturizers with sunscreen, we followed the same procedures, but we did not test after water immersion because these products don't claim to be water resistant.
Finally, we have our trained sensory panel evaluate the scent and skin feel of the products.
We found a wide variability of effectiveness against UVA rays. Seven sunscreens and one moisturizer tested just fair for UVA protection and two sunscreens tested Poor. In our tests, 18 out of 20 sunscreens did not provide the SPF (UVB) protection promised on their labels. (We found differences between the claimed SPF and the actual SPF in our tests last year as well.) That doesn't mean the sunscreens aren't protective, but you may not be getting the protection you think you are. One of the tested sunscreens rated just Fair against UVB rays and another received a Poor rating. We can't say why our test results differ from the manufacturers' claims, but they show that SPF isn't always carved in stone.
Skin cancer is the most common cancer in the U.S., and the benefits of sunscreens outweigh potential risks from their ingredients. That said, animal studies have raised some concerns about what's inside these sunscreens.
Products that contain the active ingredients titanium dioxide and zinc oxide may contain nanoparticles. These compounds have been linked to reproductive and developmental effects in animals.
Retinoids, part of the vitamin A family and an inactive ingredient in some sunscreens, have caused an increase in skin cancers in mice. There's also a risk of birth defects in people taking oral acne medications containing retinoids, though they differ from the retinoids in sunscreens. As a precaution, pregnant women may want to choose a sunscreen without the ingredient retinol palmitate or retinyl palmitate.
Research shows that people who rely on sunscreens alone tend to burn more than those who stay in the shade and wear long sleeves. Avoid the sun or stay in the shade when the sun is the strongest (10 a.m. to 4 p.m.), and dress right for the occasion. Wear a hat and clothing that's made from tightly woven fabric. (Dark colors are better at blocking UV rays.) Hold clothing up to the light; if you can see through it, the UV rays can get through, too.
When using sunscreen:
Based on our findings, it's especially important to check our Ratings for a sunscreen that did well. If you can't find a recommended sunscreen, a product rated Good will provide adequate protection.Using any sunscreen is better than using none, but it's just one part of a smart sun protection strategy.