Dermatologist Shares the Biggest SPF Mistake You're Making

Woman using sunscreen cream on the beach — LordHenriVoton / iStock

Whether you're lounging poolside, hitting the pickleball court, or going surfing, applying sunscreen is a must, as the American Cancer Society (ACS) estimates that 3.3 million people are diagnosed with skin cancer annually. However, Advanced Dermatology's sun safety study found that one in three Americans rarely wear sunscreen. More than half of participants admitted they're worried about getting skin cancer, while 65 percent said they only apply sunscreen on certain body parts. Based on participants' answers, the shoulders and back get burned the most, followed by the face and neck.

It goes without saying that the best way to prevent skin cancer is by wearing sunscreen—and by reapplying protectant throughout the day on both your face and exposed body parts, like your chest, arms, and legs. But as one dermatologist recently pointed out, it's important to understand what kind of sunscreen you're using and how you're using it.

On HuffPost's Am I Doing It Wrong? podcast, dermatologist Anthony Rossi, MD, revealed the biggest mistake people make about sunblock is confusing the "SPF" number for wearable duration.

SPF stands for sun protection factor. Just like how sunscreen comes in a lot of different forms (sprays, oils, lotions, gels, and sticks), SPF has its own unique range, too. By definition, SPF refers to the "measure of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn, damages skin, and can contribute to skin cancer," explains the organic sunscreen brand Badger.

Simply put, SPF indicates a sunscreen's strength of protection against the sun, not how long it can be worn in the sun. For instance, you probably wouldn't need to reapply SPF 15 sunblock every 15 minutes.

"We say SPF 30 or above is pretty much good for sun protection for all people because at that point of the SPF curve, at 30, it pretty much levels off," explained Rossi, who works as a surgeon at New York's Memorial Sloan Kettering Cancer Center. "So, an SPF 50 won't give you that much more protection [than an SPF 30]."

As for when you should apply sunscreen, Cheryl Peters, a senior scientist at the B.C. Centre for Disease Control and B.C. Cancer, recommends between the hours of 10 a.m. and 3 p.m. when the sun is at its strongest.

"Once you start to hit that UV index of 3, you really want to be wearing your sunscreen and reapplying it regularly," Peters said during a CBC Radio's Just Asking appearance.

And while a majority of moisturizers, foundations, and other skincare and makeup products now contain sunscreen in them, Rossi said these should be used as a "bonus" to regular sunscreen with a high SPF. Additionally, he advised opting for sunscreens with "broad-spectrum" protection.

"UVB causes burns and UVA contributes to aging, so we say 'A for aging, B for burn' — that's how we remember for our exams," Rossi said on the podcast. "Together, they can both cause skin damage. That's why you want to find a broad-spectrum sunscreen that covers both UVB and UVA."

When applying sun lotion to the face and neck, experts recommend using two fingers' worth. As for the body, a "shot glass's worth" is best, said Rossi.

If you prefer sunscreen spray over lotion, Rossi stressed that it only works if you spray directly onto the skin—not like perfume, where you spritz the air and then walk through.

"The way sunscreen is developed, you really need a good thin coat of it all over," Rossi advised. "If you're actually spraying it on your skin and you're coating your whole skin, you're getting good coverage. But you need to be diligent about it."

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Emily Weaver Emily is a NYC-based freelance entertainment and lifestyle writer — though, she’ll never pass up the opportunity to talk about women’s health and sports (she thrives during the Olympics).Read moreFiled UnderHealth Advice • News • Skincare • SummerSources referenced in this article