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Let’s face it: When it comes to sunscreen, putting it on can sometimes feel like a chore.
But even after years of lathering up before heading out to the pool or the park, many of us are still left with some questions about how sunscreen works, as well as some skepticism about some of the myths we’ve been hearing for years about skin protection.
So we turned to Dr. Melissa Piliang, a dermatologist at the Cleveland Clinic, to ask all of our silly and slightly embarrassing questions about how sunscreen does (and doesn’t) work.
What the heck does SPF actually mean?
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Sure, the acronym itself stands for sunburn protection factor, but what does that actually mean?
“If you burn after 10 minutes of sun exposure, and you put on SPF 30, then that should give you 300 minutes of sun protection,” Piliang said. That is, assuming you’re applying enough and reapplying every two hours.
How can you tell how long it will take you to burn?
There are a number of factors that go into how long it takes for your skin to burn, all of which change pretty constantly. These include your skin tone, the time of day, what time of year it is, how close you are to the sun, and more.
So if you’re trying to calculate, say, SPF 30 times the 10 minutes to burn to get 100 minutes of sun protection, you might want to just make some conservative estimates and play it safe.
Does SPF matter once you go above a certain threshold?
The difference between SPF 15, 30, and 50 isn’t as linear as you might expect. SPF 15 blocks out 93% of UVB rays, while bumping up to 30 gives you 97% protection (not necessarily double). Going up to 50 boosts you up to 98% protection. And, once you get past that point, it’s only going to give you incrementally better protection.
“Some people worry that we’re giving people a false sense of security by using those really high numbers, and maybe the additional protection is not enough, or makes them stay out longer,” Piliang said.
What does it mean when a sunscreen is waterproof?
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In 2011, the FDA decided that sunscreens couldn’t be called waterproof, since they’ll all inevitably wash off. Instead, sunscreens can be “water resistant,” meaning they have a better shot at staying effective around water.
Once you get out and towel off, most of that sunscreen will be gone, so once you’re dry (most sunscreens work best on dry skin), reapply, Piliang said.
So how much should you actually use?
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There is one benefit to using sunscreen with a higher SPF: People typically don’t use enough. When companies test for SPF, they’re using about an ounce of sunscreen for your whole body. Piliang said to think of it like the amount in a shot glass, which can hold 1.5 ounces. That’s more than most people actually use. So Piliang typically recommends a higher SPF, like 50.
“If you go a little thin with an SPF 50, it gives you a little more protection than if you go thin with an SPF 30,” she said.
Can you calm down your sunburn using sunscreen?
The first few minutes of sunburn are met with some denial (“it’s just because it’s hot out”) followed by a frantic search to figure out a way to soothe the growing pain. In these moments of desperation, it’s sometimes suggested that sunscreen itself could help.
Sunscreen typically has a moisturizer as its base, which could help ease the burn. “In a pinch, that might be OK if that’s all you’ve got. But any moisturizer would do,” Piliang said.
Sometimes, the sunscreens can contain irritants that won’t feel good against damaged skin. So if you can, pick another moisturizer that’s fragrance-free and gentle. (Preferably aloe vera for cooling the burn.)
Can you get burned if you’re sitting in a car?
- Flickr/Bruce Turner
Cars typically don’t have sunscreen protection built into their windows, which means that you’re still likely to get burnt even if you think you’re invincible behind the glass window. In studies of truck drivers, researchers have spotted that skin damage appears to be more frequent on the driver’s side (closest to the window) than on the other.
Is there a place on your body that’s most susceptible to sunburn?
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Any skin that’s exposed to the sun is at risk for damage. However, there’s a reason the tip of your nose tends to get more red: The skin that’s parallel to the sun’s rays is at even higher risk of damage. Your nose, along with the tops of your feet and the top of your head are areas where you should be extra careful and be consistent about applying sunscreen every day, Piliang said.
Does water actually intensify the sun’s rays?
- Flickr / Luis Hernandez
Yes, the combination of sun rays coming down and bouncing back off the water onto your skin do intensify your sun exposure, Piliang said. The same goes for sand and snow, which is why you should be wearing sunscreen even in winter.
If I get tan earlier in the summer, does that mean I’ll have less skin damage in August?
Getting more tan is our body’s natural response to try and shield us from the sun. But that doesn’t mean it can become your go-to sunblock later on in the summer. “It does provide you a little bit of protection, but not enough that you can back off on your sunscreen,” Piliang said. “Because you’re still going to accumulate sun damage to your skin through the tan.”
What’s the over-under on how long you can keep sunscreen?
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The sunscreen expiration date on most bottles is three years. Though if you’ve had it that long, you’re probably not using enough. Ideally, you should use up a bottle over the course of the summer. “If spring comes and you still have some left from the prior year, finish it up and then get a new bottle,” Piliang said.
Do you have to lather up 20 minutes before?
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It depends on what kind of sunscreen you have: physical or chemical blockers? A physical blocker (zinc oxide and titanium dioxide) goes into effect the minute you put it on, so there is no need to wait. Chemical sunscreens, on the other hand, do need some time to get active. So if you forget to put it on, it’s still worth it to lather up once you’re already in the sun, but maybe try to find some shade for at least the first 10 to 20 minutes.
Better yet? Just put it on when you’re getting geared up for the beach. That way, you’re not going to miss any spots and it’ll be active once you finally make it outside.
Are there any types of sunscreens to steer clear of?
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Basically, steer clear of any ones that you won’t actually use.
“The best sunscreen is the one that you will actually put on your skin,” Piliang said. If you spring for the expensive stuff but ration it out, or if it’s gloppy and you avoid putting it on, it’s not doing you any favors. But when it comes to spray-ons versus lotions, it doesn’t matter as long as you’re OK with how it feels on your skin.
What should you actually do?
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Beyond making sure you’re diligent about your sunscreen usage, Piliang suggests trying to find some shade, such as a beach umbrella, when you’re spending the day in the sun. She also recommends sun-protective clothing, hats, and sunglasses.
Apart from shielding your eyes in bright light, wearing sunglasses can also protect your eyes from sun damage, which can increase your risk for cataracts. They’ll also protect the delicate skin that’s around your eyes.