The first sunscreen mistake is not wearing any. By now, we all know spending too much time in the sun can increase risk for both skin cancer (the most common of all cancers) and premature skin aging. On top of that, a new Australian study out this week found daily sunscreen use could slow skin aging.
But even those of us with the best intentions can make mistakes when it comes to sunscreen -- mistakes that can be costly for our skin. So now that summer is almost upon us, we asked David J. Leffell, M.D., professor of dermatology and surgery at the Yale School of Medicine, and Lisa Garner, a dermatologist in practice in Garland, Texas, to sort through eight of the most common mistakes.
First, a caveat: SPF, which stands for sun protection factor, applies only to the sunburn-causing UVB rays, meaning you'll need to look for the words "broad spectrum" somewhere on the bottle to address the skin-damaging UVA rays. For more on how to choose the right sunscreen for you, click here.
You've been using the same bottle for the past three summers.
When it comes to sunscreen, expiration dates really do matter. The active ingredients in sunscreen can deterioriate over time, Garner says, which means the protection won't be as effective. What's more, an open bottle is more likely to become contaminated with germs over time, as the preservatives meant to prevent that can also lose their efficacy. You might want to read the suggested storage conditions on the label, too -- stuffing your bottle in a glove compartment or a beach-bag in the trunk might be convenient, but exposure to hot temperatures can hamper effectiveness, Leffell says.
You count on the SPF in your makeup to do the trick.
A two-in-one foundation/sunscreen certainly seems handy, but that doesn't mean it works. Part of the problem is quantity: a dab of foundation isn't the same as the amount of sunscreen you'd slather on your face. "I don't think that most women wear heavy enough makeup to get an adequate SPF from their makeup," Garner tells HuffPost. Makeup also wears off during the day ("I can't even tell I put any on this morning now that it's the end of the day," she says), and chances are you aren't religiously re-applying the way you should with sunscreen.
"It's a good belt and suspenders approach but I would not rely on sunscreen in a product that was intended for another purpose," Leffell says. In other words, if your foundation promises some added protection, great. But you still need to apply the real deal under your makeup every day.
The good news? If you're bent on a two-in-one product, moisturizer with SPF does do the trick.
You only use a dab.
When it comes to sunscreen, less is not more. But in the real world many of us don't use enough, which means the white stuff can't live up to its full protective potential. The classic rule of thumb is to slather on about a shot glass full of sunscreen to cover the whole body. The problem with that advice, though, is that a 110-pound woman is going to have less surface area than, say, a 250-pound man, Leffell explains. "I avoid giving specific amounts," he says. "Use enough to evenly cover the skin and massage it in, and be systematic about it."
When in doubt, slather more on: Both experts agree there's no such thing as too much. "It's always more than you think you should put on," Garner says. (She also recommends the "teaspoon rule" to figure out how much to apply on exposed skin when you're clothed -- for more on that click here.)
You put your sunscreen on at the beginning of the day -- and forget about it after that.
"If you're in the sun, your sunscreen is good for a max of two hours, and depending on the sunscreen it might not even last that long," Garner says. The skin literally "uses up" the active ingredient in the lotion over time, meaning it can't do any more. Sweating and swimming causes the sunscreen to wear off even faster, so consider reapplying every hour in those conditions. And be sure to let the reapplied sunscreen soak into the skin for a few minutes before diving back into the water, otherwise it'll wash right off.
You count on waterproof sunscreen when you're swimming.
Turns out, there isn't such a thing as "waterproof" sunscreen. In fact, a relatively recent iteration of FDA rules no longer even allows the word to be used on sunscreen bottles (along with "sweat-proof" or "sunblock"). Instead, based on testing, they can claim to be "water resistant" for either 40 or 80 minutes. After that? Reapply, reapply, reapply. "I can't tell you how many patients come in and say, 'But I put my sunscreen on,'" Garner says. "[But] did you put it back on?"
You only apply sunscreen on sunny days.
A cloudy day is not a sunscreen hall pass. Just because you can't see (or feel the heat from) the sun doesn't mean it's not doing damage. "UV penetrates through haze and fog and you can easily get a sunburn," Leffell says. "UV radiation is invisible: you can't smell it, taste it, hear it, see it." And that means it doesn't necessarily need to be warm or sunny to cause some real damage, whether or not you see it.
"People only think they need to put sunscreen on when it's hot," Garner says. "It never fails that here in Texas I see several sunburns in March."
UVA rays, which penetrate the skin more deeply and are a culprit in skin aging, in particular, can reach the skin even through thick clouds (and glass, for that matter).
You shell out the big bucks for the highest SPF possible.
Many skin experts recommend using a sunscreen that carries an SPF of at least 30. So does that mean SPF 60 is twice as protective, or lasts twice as long? Nope, according to the experts. An SPF of 30, when applied in the appropriate amount, will block out about 96 percent of the sunburn-causing UVB rays from the sun, Garner says. As you go up from there, you only see a very small difference (about 98 percent with SPF 50 and still under 99 percent with SPF 75) -- there's no way to block out 100 percent of the sun's rays with sunscreen.
If you feel more comfortable with those extra couple of percentage points, go for it. But it doesn't change how often you'll need to reapply or how long you can be in the sun.
You count on sunscreen for total sun protection.
Your sunscreen can't block out 100 percent of the sun's UVB rays, and it shouldn't be your only defense against sun damage. "Sunscreen does not protect you completely from the sun," Garner says. The rest of the work -- wearing a hat, sunglasses and protective clothing and avoiding the sun during the most intense hours -- is up to you.
Remember, too, that sunscreen isn't a free pass to spend the day baking in the sun. "Sunscreen should be used to protect you when you have to be in the sun during the intense part of the day," she says. "It should not be used to allow you to be in the sun longer just because you want to." And avoiding a burn doesn't mean you've properly protected your skin, she adds: "Once you've tanned, you've damaged skin."