If you want to know which headphones will stay in your ears when you go for a run or which books you should bring to the beach, the customer reviews on Amazon.com can offer helpful advice. But if you'd like to know which sunscreens are best equipped to reduce your risk of skin cancer, you might want to check with a doctor instead.
Keep in mind that it doesn't take much for a sunscreen to win endorsement. Dermatologists have only three requirements: A sunscreen should have a Sun Protection Factor (or SPF) of at least 30; it should protect skin against both UVA and UVB rays; and it should be resistant to water, including sweat.
About 5.5 million Americans develop nonmelanoma skin cancer each year. These squamous cell and basal cell skin cancers generally are treatable and rarely spread to other parts of the body, according to the National Cancer Institute.
An additional 76,000 Americans are diagnosed with melanoma each year. Although these account for only 2% of skin cancer cases, they cause the most deaths.
Altogether, the proportion of Americans who have had some type of skin cancer is about five times greater than the proportion of Americans who have had breast or prostate cancer, according to a report from the Archives of Dermatology.
Most people certainly realize they should wear sunscreen. And yet only about 3 in 10 adults use it or take other measures to protect themselves from the sun's UV rays, experts say.
To get some insight into what makes sunscreen appealing, researchers from Northwestern University examined customer reviews on Amazon.com, where about 9% of all sunscreen is purchased. Among the 6,500 sunscreens available on the site, researchers focused on the 1% with the highest customer ratings.
Of these 65 sunscreens, seven (or 11%) did not have an SPF of at least 30, five (or 8%) did not protect against both UVA and UVB rays, and 25 (or 38%) were not designed to withstand water or sweat.
Digging deeper into the top 1%, the researchers focused on the 10 with the most customer reviews — a proxy for popularity — and found that half of them weren't water-resistant. That meant they flunked the dermatologists' test.
After analyzing the top-rated comment for each of the 65 sunscreens, researchers found consumers cared more about factors like whether the product felt greasy or was difficult to rub in than they did about its effectiveness. However, effectiveness still outranked concerns about skin compatibility (i.e. whether a sunscreen caused acne) or about specific ingredients (such as nanoparticles or preservatives).
The products that made the top 1% ranged in price from 68 cents to $23.47 per ounce. In general, the sunscreens that met all of the American Academy of Dermatology's guidelines were more expensive than those that fell short, researchers found.
To the extent that online reviewers cited the endorsement of outside experts, the annual guide from the Environmental Working Group held more sway than dermatologists.
The most common reason that products in the study failed to meet the academy's criteria was that they could be rinsed away by water or sweat. However, if consumers were using these products as cosmetics or moisturizing lotions, they "may appropriately choose not to use water-resistant sunscreens," the study authors wrote.
The researchers cautioned that the features of the 65 top-rated products — and customers' feelings about them — might not be representative of sunscreens in general. Still, they noted that 30 of the 65 sunscreens on their list were among the 100 best-selling sun protection products sold on Amazon.com.
The results were published Wednesday in JAMA Dermatology.
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