Scientists Say Your Favorite Sunscreen Might Not Work As Well As You Think

If you've made it to July without getting a painful sunburn, congratulations! Now you have to keep it that way, and it turns out your sunscreen might not help as much as you think. A new study, published in JAMA Dermatology, found that many popular sunscreens don't match up with doctors' standards.

Researchers at Northwestern University's medical school looked at 65 of the most popular sunscreens on Amazon, judged by a rating of over four stars and a high number of reviews. They evaluated each sunscreen based on the American Academy of Dermatology's guidelines: broad-spectrum protection that protects against UVA and UVB rays, an SPF (sun protetion factor) of 30 or higher, and water resistance.

The results were scary for anyone who slathers on SPF at the beach: Around 40 percent of the sunscreens they tested didn't meet the American Academy of Dermatology's guidelines, and most of that was because they were not water or sweat resistant. That means if you either take a dip in the ocean or get sweaty from the heat, your sunscreen may stop being effective. Usually, a truly water-resistant sunscreen will stay effective for 40 or 80 minutes in the water.

Plus, the study found that people are paying way too much for sunscreen altogether. The cheapest product studied cost 68 cents an ounce and the most expensive cost $24 an ounce, even though they offered basically the same levels of protection. People often pay more for a sunscreen because it smells nicer, feels nicer, or is compatible with their skin type, according to the reviewers on Amazon. "You don't want to wear a chalky, greasy, terrible-smelling product, even if your dermatologist recommends it, " lead author Dr. Steve Xu said in a statement. "This gave us insight into what consumers prefer, so it can guide our recommendations and be cost conscious."

The Personal Care Products Council, the trade group that represents many sunscreen manufactures, issued a statement that noted not all sunscreens have to be water-resistant, especially if they're makeup or skincare products that happen to have SPF included. And the term "water resistant" may not mean much anyway, according to a Consumer Reports study from May. That report found that nearly half of "water resistant" products didn't stand up to being dunked in water, and many others didn't provide the SPF promised on their labels.

There was one specific sunscreen that tested well with both Northwestern and Consumer Reports: No-Ad Sport Sunscreen Lotion SPF 50. Not only did it test well, but it's also affordable, at just 72 cents an ounce. So much for your expensive, yet comically tiny, bottle of fancy sunscreen.

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