This Common SPF Misconception Is Putting Your Skin at Risk

Sunscreen is easily the most effective way to protect your skin from the sun, which unrelentingly emits damaging UV-A and UV-B rays that can cause cancer and signs of premature aging (like wrinkles, sun spots, and sagging skin). The thing is, you’ve got to know how and when to apply it well if you want to reap the full rewards of SPF. 

“Using sunscreen properly is what really keeps your skin safe,” explains Ellen Marmur, MD, FAAD, a board-certified dermatologist and founder of MMSkincare. “You should apply at least an SPF 30, apply it generously, and reapply every two hours or after swimming or sweating.” 

There are tons of sunscreen myths out there—like not needing to wear SPF if it’s cloudy or that sunscreen in your makeup is enough (both wrong)—but today we’re diving into one of the most pervasive out there!

Myth: If You Wear a High SPF, You Don’t Need as Much

One of the biggest sunscreen myths is that if you apply a higher SPF—like a 50, 75, or even 100—you don’t need to apply as much or as often. This is not the case, and failing to reapply enough every two hours will inevitably hurt your skin. We surveyed six dermatologists about this, and here’s exactly what they have to say. 

Tanya Kormeili, MD, FAAD

“Do not be fooled to think that applying SPF 50 thinly might still give you about SPF 30-level protection. That is not true,” warns Tanya Kormeili, MD, FAAD, board-certified dermatologist and founder of the Derm and Rejuvenation Institute. “The trick to better protection beyond the choice of SPF number is in the proper and adequate amount that you use. If you don’t have adequate protection, you are being irritated by UV rays. It is that simple.”

Brooke Jeffy, MD, FAAD 

“Higher SPF does not mean you can apply less or use less frequently. Think of it as a bit of a hedge against our natural tendency to not use or reapply adequately,” says Brooke Jeffy, MD, FAAD, a board-certified dermatologist. When applied incorrectly, “you do not get the level of coverage possible from the product and are more likely to experience burns and cumulative damage from radiation that leads to skin cancers, wrinkles, and hyperpigmentation.” 

Kseniya Kobets, MD, FAAD  

“Both SPF 15 and 100 will get rubbed off or sweated off, and the increased protection assumes immediate sunburn delivered, not over time as it naturally happens,” explains Kseniya Kobets, MD, FAAD, board-certified dermatologist at Montefiore Einstein Advanced Care. 

She adds, “Obviously, applying inadequate amounts of SPF will deliver lower SPF than promised on the bottle, plus it will wear away faster than two hours, putting you at risk for painful blistering sunburn, damaging your skin cells’ DNA that not only predisposes your skin to age prematurely, but also increases risk of skin cancers like melanoma (the deadlier one), basal cell, and squamous cell.” 

Alexandra Bowles, MD, FAAD

“High SPF sunscreens can offer slightly more UVB protection than SPF 30, but the difference isn’t as dramatic as many people think,” notes Alexandra Bowles, MD, FAAD, a  board-certified dermatologist at MONA Dermatology. “For example, SPF 30 blocks about 97% of UVB rays, while SPF 50 blocks around 98%, a small difference that can create a false sense of security. What matters most is applying sunscreen generously and reapplying every two hours, no matter the SPF.” 

Ellen Marmur, MD, FAAD

“SPF 30 already blocks most UV-B rays, so it’s more important how you use sunscreen than the number on the bottle,” Dr. Marmur says. “Go for the highest number SPF that you will genuinely use well enough to cover your skin. Now that formulations are more elegant, search for an SPF 50. It’s best to use a lotion for your face, ears, neck, and a spray for your body and hands and feet and scalp.” 

Nazanin Saedi, MD, FAAD

“I most commonly see SPF 30, 45 and. 50, and the difference is admittedly marginal. If you have fair skin that burns easily, melasma, rosacea, or a higher skin cancer risk, it’s always best to choose the higher SPF level,” says board-certified dermatologist Nazanin Saedi, MD, FAAD. “But regardless of what level of SPF you choose, you must reapply every two hours for it to remain effective.”