15 Biggest Sunscreen Mistakes

By now, you probably know that you should use sunscreen every day both to help reduce your risk of skin cancer and to prevent pesky wrinkles, dark spots, and other signs of premature aging. But if you’ve been following the news, you might have seen the FDA’s warning that sunscreen could potentially be dangerous. It’s true that the FDA announced that we don’t know enough about the long-term effects of some sunscreens. Dermatologists, however, still say that lathering up before spending time outdoors is a must—despite these new concerns. “Sunscreen is one of the major components of sun protection,” Noelani González, MD, an instructor of dermatology at the Mount Sinai Icahn School of Medicine in New York City, explained to Health. Yet even people who do slather it on religiously make potentially dangerous mistakes. Here are the most common ways you're messing up with sunscreen—and how to truly protect yourself from UV rays.

How many people have you seen get to the beach, spread out their blankets, strip down to their swimsuits, and then start slathering away? "You actually want to apply your sunscreen 30 minutes prior to exposure," says Jeannette Graf, MD, assistant clinical professor of dermatology at Mount Sinai Medical Center in New York. That way, it has time to get absorbed and start working—and so you don't get UV exposure for those first few minutes when your skin is vulnerable.

Skin cancer can strike anywhere, so it's best to apply sunscreen when you're buck naked. Otherwise, "if you already have a swimsuit or clothing on, you're likely to apply it gingerly so you don't get it on your clothes, which makes you likely to miss a spot or not apply liberally enough," says Noelle Sherber, MD, a consulting dermatologist for the Johns Hopkins Scleroderma Center. Strip down in front of a full-length mirror, she says, which "helps ensure you entirely cover tricky spots like the mid-back and backs of the legs." (And you should apply before going outside anyway, right?)

Just like the rest of your skin, lips are vulnerable to UV rays, so it's extremely important to use sunscreen on your mouth, Dr. Graf says. But don't use the same stuff you use on the rest of your body—it tastes weird and won't last that long on your lips anyway. So try a lip balm with SPF, which is thicker so it stays on longer. "Then reapply even more frequently than you do body sunscreen, since talking, eating, and drinking removes the sunscreen on your lips faster," she says.

Think you can smear sunscreen on your nose like a 1950s lifeguard and be covered? Unfortunately, there are a lot of less-obvious areas people tend to forget—and they're just as important to protect, Dr. Graf says. "The most commonly missed areas are toes and feet, including the bottoms of your feet; underarms; back of the neck under the hairline; ears, especially the tops and back of your ears; eyelids; and inner upper arms." Put that stuff everywhere.

The small print on your sunscreen label matters, so make sure you're choosing the right sunscreen for your activity, especially if that activity involves sweat, a pool, or the ocean. "Make sure you get a water-resistant formulation for swimming or activities where you'll perspire, because non-water-resistant formulas can slide right off," says Dr. Sherber. "Plus, they tend to mention migrate into eyes and sting, whereas water-resistant ones won't."

It's not just a marketing gimmick: There is a difference between face- and body-specific sunscreens. "Facial skin is generally more sensitive to irritation than body skin, so face formulations have been tested to cause less irritation and not trigger acne," says Dr. Sherber. "If you're acne-prone or sensitive, avoid the body versions for your face, especially the dry-touch sprays—they're absolutely full of alcohol, which is very drying and irritating for facial skin."

Danger! It may seem counterintuitive to slather on sunscreen on a gray or drizzly day, but you can get UV exposure without ever seeing the sun in the sky, says Dr. Graf. Eighty percent of UV rays still come through on cloudy days, according to the American Academy of Dermatology, so don't let the weather affect your sunscreen use.

The old rule about using a shot glass worth of sunscreen every time you apply still holds up, says Dr. Graf. (That's about 1.5 ounces.) Pros also say that a nickel-size dollop is the right amount for your face. From the neck down, 2 mg of sunscreen per square centimeter of skin is necessary, which is the equivalent of about 2 tablespoons. But now that more of us are opting for continuous spray formulas, it can be hard to tell if we're really getting enough coverage. To make sure you're using sprays correctly, she suggests holding the can six inches from skin and spraying nonstop, so you can see the moisture covering the entire area. "Then rub it in—yes, even if the bottle says you don't have to—so you don't miss spots," Dr. Graf says. "And repeat the spray a second time."

Unless you choose to spend your time in a windowless bunker, you're not protected from UV rays when you're inside. "Driving can be a major source of incidental exposure," says Dr. Sherber. "The windows and windshield block UVB rays so you don't see a sunburn, but UVA seeps right in, and that's the spectrum that causes most skin aging and skin cancer." Your best bet: apply sunscreen every morning, then feel free to sit by a window or take a drive! At the very least, try a moisturizer with SPF so you're not adding a step to your daily routine.

It used to be that many sunscreens only blocked UVB rays, the high-energy kind responsible for sunburns. But shielding against UVA rays is just as important, says Dr. Graf, because they "penetrate the skin more deeply, are constant throughout the year, and cause premature aging." Umm, no thanks! To be fully covered, look for sunscreens labeled "broad spectrum," which means they thwart both types of rays. And good news: these formulas are increasingly becoming the norm.

The SPF (sun protection factor) measures how well the sunscreen blocks out UVB rays—which are primarily what cause sunburns. The number tells you how long it would take to redden your skin versus the amount of time without it. For example, with SPF 15, it will take you 15 times longer to burn than if you were wearing nothing. So what number should you aim for?

• Yes, tanning oil with SPF 8 technically is sunscreen, but it's just not enough protection. The Skin Cancer Foundation recommends using broad-spectrum sunscreen with at least SPF 15. But should you go higher? Some say the often-pricier high-SPF sunscreens are a waste of money, since they don't provide much more protection—SPF 30 blocks 97% of rays, while SPF 50 blocks just 1% more. However, they do have some benefit.
• "They absorb more free radical-producing energy, so I recommend them for the summer," Dr. Graf says. One caveat before you reach for the SPF 100: "The super-high SPFs can provide a false sense of security, like you're protected for longer, but you need to reapply just as often as you would an SPF 30."

If you're using enough sunscreen when applying—remember that shot glass-worth, or those two coats of spray?—then having bottles leftover from years past shouldn't be much of an issue. But if you happen to have sunscreen that's been lingering for two years or more, Dr. Graf says to chuck it, since it can lose its effectiveness over time.

Shelf life varies from two to three years, depending on the formula you choose. Look at that date before you make your purchase, and continue to pay attention to it. The reason: Sunscreens don’t always show obvious signs they are past their prime. Dr. Elizabeth Hale, MD, a dermatologist in NYC and senior vice president of the Skin Cancer Foundation, also advises keeping track of where your bottle has been, saying “exposure to UV light and heat can degrade a product a lot faster. Avoid leaving a bottle in the car or in direct sunlight or even the bathroom, which tends to get humid.”

It may feel like you did your due diligence by applying sunscreen once, but it's not a day-long cloak of immunity. Reapplying it is just as important as putting it on in the first place. How often? "Every 80 minutes, even if it's water-resistant," says Dr. Graf.

You should be layering on more SPF every two hours. And if you’ve gone for a swim (even if your SPF is water-resistant!) or have been sweating excessively, reapply immediately after those actions. To be sure that you’re covered head to toe, pros recommend applying sunscreen before you get dressed and then reapplying to all exposed skin.

Seeking solace under a beach umbrella or an awning near the pool doesn't mean you're getting adequate protection from the sun. Why? Sand and water both reflect damaging rays, and 34% of UV radiation gets through when you're under a beach umbrella, "so you still have to apply sunscreen if you're sitting under cover," says Dr. Graf. Even if you don't get a sunburn, you're still getting UV exposure.

Sunglasses aren't just a fashion statement—they're critical to keeping your eyes safe from UV rays. Make sure your sunglasses offer UV protection, because some inexpensive styles don't have the protective coating. "Without it, the dark lenses actually allow your pupils to dilate, allowing even more UV rays in, which can play a big role in cataract development," says Dr. Sherber. Finally, a health reason to buy a pair of nice shades!