The Truth About How Often You Need to Reapply Sunscreen, According to Dermatologists

·5 min read
Photo credit: PeopleImages - Getty Images
Photo credit: PeopleImages - Getty Images

It’s day two of your beach vacation, and you notice a hot, painful tenderness come over your skin. It can only mean one thing—you forgot to reapply sunscreen and now you’re sunburned.

It happens to the best of us (no matter how diligent we are). Problem is, forgetting to reapply sunscreen can lead to more than an uncomfortable skin rash: Having five or more sunburns doubles your risk for melanoma, the deadliest form of skin cancer, according to the Skin Cancer Foundation.

The best way to reduce your risk of sunburn and skin cancer? You guessed it—wearing sunscreen (putting on a wide-brimmed hat and sun-safe clothing is a good idea, too). Using a sunscreen of at least SPF 15 every day can reduce your risk of developing squamous cell carcinoma by about 40% and melanoma 50%, per the Skin Cancer Foundation, but you should apply at least SPF 30 if you’ll be outdoors.

Now, all you have to do is remember to slather it on—and reapply. Here’s how to make a habit out of it, according to dermatologists.

How does sunscreen work, again?

There are two types of sunscreen: those with physical or chemical blockers. Physical (or mineral) sunscreens contain ingredients like zinc oxide or titanium dioxide that sit on the skin, physically preventing UV rays from penetrating it. Chemicals sunscreens have ingredients such as avobenzone and octisalate, which absorb UV rays before they can harm your skin. Physical sunscreens may be less likely to cause skin irritation, but both types are safe and effective, according to the Skin Cancer Foundation.

To understand how sunscreen works (no matter which type you choose), think of it like a cup that gets filled by the sun’s rays, says Heather Woolery-Lloyd, M.D., a board-certified dermatologist and director of Ethnic Skin Care at the University of Miami Department of Dermatology. After a few hours, the cup gets full and can’t absorb any more rays so they go into your skin instead. “Reapplying sunscreen is like putting out a fresh cup to absorb the sun’s rays, rather than letting it get into your skin,” Dr. Woolery-Lloyd explains.

How often should you reapply sunscreen?

To stay protected all day, you need to reapply every two hours, says Dr. Woolery-Lloyd. If you’re swimming or sweating a lot, you’ll need to reapply more often.

And don’t be afraid to be liberal with your application. Most people don’t apply enough sunblock in the first application, so they aren’t getting the same level of protection as stated on the label, says Leslie Baumann, M.D., a board-certified dermatologist, researcher, and founder of Baumann Cosmetic Dermatology. “This makes the sunscreen less effective, causing it to lose its ability to protect the skin,” she notes.

Think you can skip sunscreen when it’s cold or cloudy outside? Not so fast. Ultraviolet light, including UVB rays that damage your skin, may be less present on a cloudy day but UVA rays are just as strong and cause more skin damage, says Dr. Baumann. In other words, you still need to wear sunscreen during rainy days or even cold weather activities like skiing.

When should you reapply sunscreen more frequently?

As a general rule, reapplying sunscreen every two hours will protect you from the sun’s harmful rays. But there are a few situations where you may want to reapply more often:

When you’re driving

“People underestimate how much sun exposure they get when they’re in the car,” Dr. Woolery-Lloyd says. Whether you’re the driver or a passenger, there’s a good chance you’re in direct sunlight, so you definitely want to abide by the two-hour reapplication rule. Dr. Woolery-Lloyd says she tells her patients to be extra cautious during long commutes.

When you’re swimming

Water-resistant sunscreens are great but they still need to be reapplied every two hours. You should also reapply sunscreen every time you dry off with a towel. When you wipe away the water, you’re also wiping off your sunscreen.

When you’re sitting next to a window

You’re not safe from the sun’s rays just because you’re indoors; windows actually make it easy for the sun rays to get to you, whether they’re open or closed. “If your office has a window, you can bet that you’re actually getting quite a bit of sun,” Dr. Woolery-Lloyd notes. So if you’re sitting by a window for an extended period of time, follow the sunscreen rule and re-up every two hours (or more).

How to remember to reapply sunscreen

It’s easy to forget to reapply your sunscreen, but there are things you can do to help you remember. To get into a daily habit, try adding it to your regular routine. “Apply sunscreen in the morning after you brush your teeth, then apply it again before you go to lunch or anytime you are headed outside,” Dr. Baumann suggests. Don’t forget areas like your ears, neck (front and back), chest, and the top of your hands.

Above all, find a sunscreen you love, especially for your face (since reapplying here can be a bit tricky). If you actually like the formula, you’ll be more likely to stick with it. There are tinted sunscreens that offer light coverage, moisturizers with SPF if you like to go bare-faced, and powder sunscreens that make reapplying over makeup easier than ever.

You can also try using apps like QSun and My Skin Track UV to remind you. “These apps are great for not only tracking how much sun exposure you’re getting, but also for telling you when you need to reapply sunscreen,” Dr. Woolery-Lloyd says. In other words, they’ll help you have fun in the sun—safely.

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