The Illuminating Truth About SPF

There’s a lot of hype and hysteria out there, so you can’t believe everything you read about sunscreen—unless it’s the information on the following pages. Our guide is all you’ll need to protect yourself with confidence and still enjoy a beautiful summer day


The Internet is good for looking up restaurant reviews, but not always so great for sussing out which information is real and which is just…wrong. There’s no better example than the conversation around sunscreen. Some natural beauty bloggers want you to believe that it’s toxic and can
do more harm than good; others insist SPF doesn’t even protect you from skin cancer. Both misconceptions can have deadly consequences. “It feels like I’m constantly counseling patients on proper sun habits and debunking myths that have very little basis in medical science,” says Mona Gohara, M.D., associate clinical professor of dermatology at the Yale School
of Medicine. “This fake news is one reason why many people aren’t wearing sunscreen regularly—that’s not a good thing.”

What we do know? Shielding your skin daily from both forms of ultraviolet radiation generated by the sun—UVB and UVA rays—is easily one of the best ways to look younger and stay skin cancer-free. For more truths, we asked top dermatologists and product formulators to give us their insights on what to use, how to get the best protection, and when to tune out the chatter.

The genesis of this bogus claim is one decades-old rodent study. It found that mice who were fed oxybenzone, a commonly-used UVB filter, had an increase in uterine weight, leading some to believe that this ingredient can mimic estrogen in the body and potentially increase a person’s risk of various cancers. The experts we spoke to say that’s too big a leap. “There is not a single human or animal study showing any direct correlation between approved sunscreen ingredients and any form of cancer,” says Gohara. Case closed.

Still, to get adequate protection, do your homework. Avobenzone is the only chemical approved to block the full spectrum of UVA radiation, so any product you pick up must contain this ingredient (unless your lotion of choice relies on mineral blockers; more on that below). What’s more, some ingredients don’t play well together: One study found that, when paired together in a formula, octinoxate, another common sunscreen chemical, can actually destabilize avobenzone, rendering it potentially useless against cancer-causing UVA radiation. “Brands who use these ingredients in their formulas include other stabilizing ingredients to counter these effects, so the final formulation will pass the stability and UVA test,” says Steven Wang, M.D., director of dermatologic surgery and dermatology at Memorial Sloan Kettering Cancer Center in Basking Ridge, NJ.

The bottom line: the best sunscreen is one that you’ll slather on regularly, says Gohara.

While formulas with mineral blockers such as zinc oxide or titanium dioxide (what most people think of when they say “natural sunscreen”) have come a long way, many can still leave an unflattering whitish cast on skin—one reason consumers, especially people of color, discontinue their use.

If you’re insistent upon shopping around for one of these formulas, you should also know that, in this case, the word “natural” may be a bit of misnomer. “The only forms of titanium dioxide or zinc oxide approved for use in sunscreens in this country are made in a lab,” says cosmetic chemist Perry Romanowski. “So if you’re using a product with this ingredient, chances are it’s synthetic.” If you’ve honed in on a formula with only zinc oxide, scan the rest of the label too—just because the active ingredient is naturally derived doesn’t mean there aren’t chemical preservatives, thickeners, fragrances, and other additives making up the rest of the formula. “These days, finding a product that is 100 percent naturally derived is a very difficult task,” says Romanowski.

You wear SPF to prevent redness, so why do some leave you with an itchy scarlet rash? It may have nothing to do with the sunscreen ingredients themselves, says Sandy Skotnicki, M.D., assistant professor of dermatology at the University of Toronto and an expert in allergic skin reactions. “True sunscreen allergies are extraordinarily rare and usually oxybenzone is the culprit,” she says. “If you experience any redness or stinging, it’s far more likely an irritant reaction, which can be due to synthetic fragrances or preservatives that are added to the formula.” Look for formulas labeled “fragrance-free” (“unscented” products may simply mask the smell of raw materials with odor-neutralizing chemicals, which can still be irritating) and avoid preservatives like parabens, phenoyethanol, and sodium benzoate, says Romanowski.

Slathering it on while enjoying the surf is a smart move, for sure. But our experts are adamant that incremental sun exposure has a cumulative effect on the development of skin cancers, especially basal and squamous cell carcinomas, the two most common forms of the disease. Daily sunscreen use is key to slashing this risk. The proof: One Australian study of more than 1,600 people published in the Journal of Clinical Oncology found that those who wore sunscreen every day had 50% fewer instances of skin cancer than those who wore it only intermittently. “UVA rays can penetrate cloud cover and windows, so you’re getting exposure even when you think you’re in the clear,” says Wang.

What’s more, a growing body of research is showing that visible light—waves emitted from lightbulbs, television screens, and computer monitors—can also age skin. “I recommend that patients apply their SPF moisturizer in the morning and then touch up throughout the day with a powder sunscreen with iron oxides, which we know protect from all wavelengths of light,” says Gohara.

Sunscreen skeptics have argued that since the deadliest form of skin cancer can pop up where the sun don’t shine (lesions have been identified on toes, inside belly buttons, and even on the genitals), the correlation between sun exposure and skin cancer has been overstated. “Sun exposure is responsible for 95 percent of all skin cancers, including melanoma,” says Wang.

So what’s the cause of the other five percent? There are a few explanations: Any thermal burn—let’s say you scorch yourself on a hot pan—can damage skin and, in extremely rare cases, trigger a mutation that can lead to skin cancer. And other diseases like HPV can be precursors to skin cancer. Wang also offers this: “It’s possible that sun exposure decreases overall immune response and causes additional damage to previously compromised skin cells elsewhere on the body. This can lead to an accumulation of mutations in the cells and accelerate the progression to skin cancer.”

A recent study published The Journal of the American Academy of Dermatology found that participants wearing a product with an SPF of 100 or more experienced fewer sunburns than those using the same amount of an SPF 50. “Most people don’t use enough sunscreen, and a product with a higher sun protection factor can make up for that deficit,” says Skotnicki.

But don’t be fooled into thinking that a 100-plus product is shielding you from 100 percent of the sun’s rays. “The SPF number is merely a measure of how much longer it takes for you to get burned when using the product, so wearing SPF 30 means it will take thirty times longer and so on up,” says Gohara. Your best bet if you’ll be soaking up rays all day long? Pair sunscreen with an umbrella or UV-protective clothing, and head indoors for lunch.

MYTH: YOU’LL BECOME VITAMIN D DEFICIENT IF YOU WEAR IT. While it’s true that unprotected sun exposure is a good way for your body to replenish its vitamin-D stores, any number of factors—poor diet, disease, obesity—can contribute to lower levels. And one recent study of nearly 100 Hawaiian surfers who reported that they typically get nearly 15 hours of sun exposure per week demonstrated a wide range of D levels, with some subjects deficient. “If your levels are low, just take a supplement,” suggests Wang. Try 2,000 to 3,000 IUs of D3 (the most potent form). Of course, check with your doctor before beginning any vitamin regimen.


Many brown-skinned people are still under the misconception that they don’t need to use sunscreen. In fact, 65 percent of African Americans surveyed in a recent poll copped to never using the stuff. It’s time for a reality check: “Fairer types are more prone to cancer, but medium brown skin only has an SPF of about 13, so it still needs protection, too,” says Gohara, who is of Egyptian descent.