From Head to Toe: Your Complete Guide to Sunscreen Reapplication

Plus, how to remember when it's time to slather on that SPF for a second, third, or even fourth time.

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woman applying sunscreen at the beach
Photo: LeoPatrizi / Getty Images

It always bears repeating: Applying sunscreen each and every day is a must, regardless of the time of year or the weather outside. Reapplication is just as important. As New York City-based dermatologist Dr. Hadley King points out, if you don't reapply regularly, you won't experience the full SPF of the product all day long. At the height of summer, when you're spending time on the beach or in your backyard, you need full coverage around the clock. Read on to learn more about reapplying sunscreen, including why it matters, how to remember, and the best methods for doing so.

Reapplication really matters.

The sunscreen you applied at the start of the day will not see you through to its end. According to board-certified dermatologist Dr. Tiffany J. Libby, whatever the SPF number on the bottle, protection is only effective for 120 minutes; therefore, she recommends reapplying (liberally!) every two hours. This is especially important if you're exercising or engaging in water sports, as these activities cause you to sweat or rinse off your SPF. "One thing you should absolutely look for on your sunscreen bottle is 'water-resistance'—the label will either say water resistant for 40 or 80 minutes," Dr. Libby shares, noting that no formula, however, is truly waterproof.

Sweating or swimming? Reapply more frequently.

With this in mind, if you are partaking in outdoor activities that wear down your SPF application, Dr. Libby says to reapply directly afterwards instead of waiting for the two hour mark. Need a reminder to do so? She advises setting a timer on your phone or opting for Blue Lizard's Sunscreen with Smart Bottle Technology ($14.98, "The bottle or cap changes color in harmful UV light as a reminder to reapply," she notes.

Get dry before you reapply.

Before slathering yourself in your favorite SPF, take a moment to towel off. Whether you just finished a tennis match, came to a halt after a long run, or hopped out of the pool or ocean, ensure that your skin is fully dry before you reapply. "Applying sunscreen to wet skin reduces the efficacy of the SPF protection, because it will not be evenly applied," notes Dr. Zain Husain, the founder of New Jersey Dermatology and Aesthetics Center. Additionally, board-certified dermatologist Dr. Terrence Keaney, the founder of SkinDC, says to opt for stickier sunscreens (often marketed as "sport" formulas), as they're more likely to adhere to your skin during physical activity.

Use enough enough product.

Don't use less sunscreen when you reapply—treat a second or third application exactly like you would the first. "Most people don't apply enough sunscreen. Make sure that you use about a shot glass-size worth of sunscreen for your entire body," Dr. Husain says, noting not to forget about commonly overlooked areas, like the scalp, lips, ears, back of the neck, and feet.

Be prepared to wait 15 to 20 minutes before diving back in.

You need to give this new coat of SPF time to sink in—especially if you're swimming. Jump back into the water too quickly, and your fresh layer of protection will wash away with the waves. "For mineral sunscreens that work right away, you can go swimming after the sunscreen is fully rubbed in and has time to dry," Dr. Libby says. "I find this usually takes around 15 to 20 minutes. Chemical sunscreens take some time to work after they are applied, so I would follow the same rule of thumb of waiting around 20 minutes before swimming."

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