The Exact Right Time To Apply Sunscreen Before Sun Exposure, According to Dermatologists

Most of us know we should be wearing sunscreen every day, but many of us still apply it only after we feel a little crispy at the beach or by the pool.

Knowing when to put on sunscreen, or exactly how long prior to sun exposure it needs to be applied, is important too. Apply it too late and you may not be getting the protection you think you are. Skip reapplication and the coverage you started off with won’t last.

The timing question matters more than many people realize. Sunscreen needs a little time to set before it can do its job properly, and that window may vary slightly depending on whom you ask, but dermatologists generally agree on a specific range of time before you head outdoors.

Equally important, though, is how much sunscreen you’re putting on and whether you’re reapplying it throughout the day. To break it all down, we asked two board-certified dermatologists to weigh in: Dr. Mona Foad, board-certified dermatologist and founder of MONA Dermatology, and Dr. Susan Massick, Associate Professor of Dermatology at The Ohio State University College of Medicine.

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How Long Before Sun Exposure Should You Apply Sunscreen?

The window dermatologists recommend is 15 to 20 minutes before you step outside. This is enough time for the product to settle and form a barrier across the skin.

“For most sunscreens, I recommend applying them about 15 minutes before sun exposure,” Foad tells Parade. “This allows the product to form an even protective film across the skin and ensures you’re getting the intended level of protection before stepping outdoors.”

If you want to be extra sure, make it 20.

“I usually allow at least 20 minutes from sunscreen application before heading out the door to allow optimal protection,” Massick says. “If you wait to apply while you’re already outside, your sunscreen won’t be absorbed enough to be as protective as it could be.”

The key takeaway is to put on your sunscreen before you leave the house, not once you’re already having fun in the sun. Those few minutes make a real difference in how effectively your skin is protected.

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Does It Matter How Much Sunscreen You Use?

Timing is only half the equation—how much sunscreen you apply matters just as much. “Many people apply sunscreen at the right time but not in the right amount,” Foad says.

“I typically recommend using approximately a nickel-sized amount for the face and remembering to cover commonly missed areas such as the ears, neck and chest,” she continues.

For the rest of the body, you need at least one ounce, or about a shot glass full of sunscreen.

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How Often Should You Reapply Sunscreen?

Unfortunately, even if you get the initial application right, it won’t keep you protected all day long. Reapplication is non-negotiable, particularly during extended time outdoors.

“Sunscreen should be reapplied every two hours, and more frequently after swimming or excessive sweating,” Foad tells Parade.

The best sunscreen routine is one you actually stick to, Massick says. And the best way to stick to it is to build reapplication into your day the same way you’d schedule any other part of your routine.

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Common Sunscreen Mistakes To Avoid

Even people who wear sunscreen regularly make mistakes that leave their skin less protected than they think. As the experts discussed, applying it too late, using too little and skipping reapplication are the three most common errors, but all three are easy to fix once you know what to watch for.

Another common problem is forgetting sunscreen on the toes, hands, backs of knees, chest, back of the neck and other spots people accidentally skip, leaving frequently sun-exposed skin unprotected even when the face is covered.

Related: 12 Best Moisturizers With SPF To Keep Your Skin Hydrated and Protected, Tested by Dermatologists

Does the Type of Sunscreen Impact How Early You Should Apply It?

The type of sunscreen matters less than these good application techniques.

“The best sunscreen is one that is applied consistently, generously and reapplied when needed,” Foad says.

The experts do also recommend a broad-spectrum sunscreen, meaning it protects from both UVA and UVB ultraviolet radiation. UVA rays have a longer wavelength that can penetrate deeper into the skin and cause inflammation, wrinkles and skin cancer. UVB rays are shorter and more direct, but can lead to DNA damage that also causes skin cancer.

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Sources:

• Dr. Mona Foad, board-certified dermatologist and founder of MONA Dermatology
• Dr. Susan Massick, FAAD, Associate Professor of Dermatology, Department of Dermatology, The Ohio State University College of Medicine