If you miss one, you increase your risk of skin cancer
Using sunscreen might not be as simple as you think: Most people hold inaccurate beliefs about their sunblock, new research from the American Academy of Dermatology (AAD) suggests.
In fact, the increase in protection from an SPF 15 to an SPF 30 isn’t very significant.
An SPF 30 blocks 97 percent of sunburn-causing UVB rays, while an SPF 15 blocks 93 percent, says Josh Zeichner, M.D., a spokesman for the AAD.
That means an SPF 30 blocks only 4 percent more UVB rays than SPF 15 does, a far cry from the “double” the numbers behind them would have you believe.
And these misconceptions might leave you at greater risk of developing skin cancer.
In the survey, only 32 percent of respondents knew that an SPF 30 sunscreen does not provide twice as much protection as an SPF 15 sunscreen does.
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The real deal: Any sunscreen, no matter the SPF, wears off after two hours.
Putting too much faith in high SPF—whether it’s for amount of protection or how long you can safely stay in the sun—can be dangerous, since it can lead to a false sense of security regarding your burn risk, says Dr. Zeichner.
That may mean you might be more likely to stay in the sun for longer than you should or put off reapplying more sunscreen, which can make you more likely to get sunburned.
Your move, then, is to follow these 6 simple rules when using your sunscreen.
1. Choose a sunscreen with an SPF of at least 30, says Dr. Zeichner. (The 4 percent difference of UVB rays blocked from SPF 15 to SPF 30 can add up over time, so SPF 30 is the recommended minimum.)
2. Make sure it says it’s “broad spectrum,” which means it also protects you from both cancer-causing UVB rays and prematurely-aging UVA rays.
3. Apply it 15 minutes before you go out in the sun.
4. Reapply every two hours, or sooner if you’re swimming or working out.
5. Use about one ounce, roughly equivalent to a shot from a stingy bartender.
6. And do so generously: If you don’t apply enough of the sunscreen, the SPF level can become diluted, says Dr. Zeichner. And that may make you more likely to burn.