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What Number SPF Should You Wear? Your Burning Sunscreen Questions, Answered

Protecting your skin from sun damage is both a beauty and a health issue.


There’s one quick way for fun in the summer sun to turn sour: a sunburn. In addition to being painful, sunburns can be dangerous. There are two types of sun rays that can damage the DNA in your skin cells, and it’s important to protect your skin from both: UVB rays cause sunburn and play a key role in developing skin cancer, while UVA rays cause skin damage and can lead to aging and wrinkles, in addition to a nice tan. Lucky for us, there’s a simple defensive solution: sunscreen! 

Some of the earliest sunscreen products emerged in the 1930s. Australian chemist H. A. Milton Blake produced a sunburn prevention cream after experimenting in his kitchen, and a Swiss chemistry student named Franz Greiter created a sunscreen after getting burned while mountain climbing. Greiter is also credited with establishing Sun Protection Factor (SPF) as the standard for measuring how long a sunscreen will protect you from the sun’s UVB rays. While wearing SPF 30, for example, it’ll take you 30 times longer to burn than if you weren’t wearing any sunscreen any all. 

Many ancient societies, from Egyptians to Romans, had their own methods of blocking the sun’s rays. They enlisted the help of natural ingredients, from plant extracts to rice bran, jasmine, and olive oil. Of course, back then little was known about skin cancer or aging (one of the main causes of premature aging is sun exposure), so these were mere beauty measures — sunshine led to tanned skin, and pale skin was considered more appealing. These people unknowingly protected their health while guarding their beauty. 

Back here in modern times, you may still need help figuring out what SPF to wear. We asked Dr. Rachel Westbay, Board Certified Dermatologist at Marmur Medical, six burning (pun intended) questions about sunscreen application.

How High Should My SPF Go?

To protect yourself first and foremost, Dr. Westbay recommends that you begin with the use of a broad-spectrum sunscreen. This type will shield your skin from both UVA and UVB rays. “The sunscreen should have an SPF of 30 or higher, which blocks 97 percent of the sun’s UVB rays,” Dr. Westbay advises. “Higher-number SPFs block slightly more of the sun’s UVB rays, but no sunscreen can block 100 percent. It is also important to remember that high-number SPFs last the same amount of time as low-number SPFs.” 

Should I Increase My SPF Depending on Where I Live?

You might think that applying sunscreen is overkill the winter, but if you plan to hit the slopes or even take your dog out for a chilly stroll, be cautious with your sunscreen application. “Even if you’re in a location that’s cloudy or snowy, wearing sunscreen is a crucial part of maintaining your skin health and happiness,” Dr. Westbay cautions. “UVB rays are one of the main causes of sunburn and those happen to be the rays that are the strongest in the summertime — but that doesn’t mean they just disappear during the winter. UVB rays can harm your skin year-round.”

If you’re skiing in the mountains, your risk may be even greater. “UVB rays can be more harmful at higher altitudes and when reflecting off of surfaces like ice or snow,” Dr. Westbay points out. “In fact, snow reflects up to 80 percent of the sun’s UV light. That means it can hit you twice, increasing your risks of skin cancer and skin damage.” Ultimately, Dr. Westbay doesn’t believe geography should dictate your sunscreen use — after all, you’re no safer in warmer climates, as “UV levels are higher closer to the equator because the sun’s rays have a shorter distance to travel through the atmosphere.” Ultimately, the risk of skin cancer from UV radiation exists no matter the climate or proximity to the equator.

Does My Skin Color Make a Difference?

What about people with darker skin tones? They burn less easily than pale folk, so do they really need to worry about all this? “The natural SPF protection from a darker complexion is not enough to protect against UVA rays or UVB rays, both of which play a role in skin cancer formation,” Dr. Westbay warns. “The most SPF that skin itself can offer, irrespective of skin tone, is about SPF 13. Plus, not only can you get skin cancer when you have skin of color, but the outcomes are often worse, largely due to delay in detection or presentation — so this is especially important.” If you have darker skin, your body requires the same protection as lighter skin; and in addition, you should exercise extra diligence when it comes to skin cancer screenings

When Should I Reapply Sunscreen?

Sure, it’s a pain to rub sunscreen in once — but reapplying it when you’re on the beach or at a party can really feel like a drag. It’s important, though, because your protection will inevitably fade. Even a high-number SPF requires reapplication if you’ll be spending additional time outdoors, Dr. Westbay advises. “Ideally, the formulation you use should be water-resistant and the sunscreen should be reapplied every two hours (or sooner) if swimming or exercising.”

Can I Use a Moisturizer/SPF Combo?

Since skin tends to get extra dry in the heat of summer (and a sunburn will make it even worse), you may be tempted to use a moisturizer/SPF combo — but Dr. Westbay advises against these. “I prefer my patients use both a moisturizer and a separate sunscreen, though I obviously prefer them over no SPF at all,” she explains. “It’s not so much an issue of product penetration and more a concern regarding the sunscreen’s ability to actually provide the SPF listed on its label, because mixing it with a moisturizer dilutes the formula. So, a product listed as an SPF of 15 may only be giving you an SPF of 10-12 in a moisturizer combo.” Sounds like it’s best to steer clear of the combo and purchase these two products separately.

How Else Can I Protect My Skin?

According to Dr. Westbay, additional safety measures may include wearing protective clothing and accessories, like hats (particularly key for anyone with hair thinning) and UV blocking fabrics, which are rated by a system known as UPF (check out some sun protection clothing here). Take advantage of your summer and make hay while the sun shines — just don’t forget to shelter your skin before you begin!

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