What Does SPF Stand For? We Asked Dermatologists

Those with tanning goals for summer might be considering foregoing sunscreen to acquire their base layer, but shirking SPF may not be such a good idea. Unprotected sunbathing can lead to burning and redness, and sunburn can also be aggressive enough to cause painful blistering and scarring, says Rachel Nazarian, MD, a New York-based dermatologist and fellow of the American Academy of Dermatology. Even worse, repeated exposure could put you at risk of cellular mutation, which may lead to skin cancers, including melanoma and basal cell and squamous cell carcinoma, she adds. Yikes.

Not wearing sunscreen is also doing your skin and anti-aging routine a huge disservice. Long-term exposure to the sun without SPF protection can lead to the breakdown of collagen and elastin—proteins in the skin that are responsible for the youthful, full, and bouncy appearance of healthy, young skin. Sun-damaged skin can trigger wrinkling, sagging, sunspots, freckles, dark pigmentation (like melasma), enlarged pores, and broken blood vessels, she notes.

So what level of sun protection do you really need? Here’s everything you need to know about SPF.

What does SPF stand for exactly?

SPF literally stands for sun protection factor, which measures a sunscreen’s ability to protect the skin against UVB rays (the ones that cause sunburn), Joshua Zeichner, MD, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City, tells Health. When you see broad spectrum on a sunscreen bottle, it means that the product also protects the skin against UVA rays, which cause skin aging, skin damage, and skin cancers, he adds.

How does SPF work?

Ultraviolet blockers are divided into two main categories: chemical and mineral. Chemical blockers absorb UV light—converting it into heat and preventing it from penetrating the skin—and mineral blockers actually reflect the light away from the skin, Dr. Zeichner explains. But which one does a better job of protecting your skin? Both provide excellent protection, so it really comes down to personal preference, he says.

While many might reach for sunscreen with chemical blockers—since mineral sunscreens tend to feel heavier during application and leave a white tint, Debra Jaliman, MD, a dermatologist based in New York City, prefers mineral (also known as physical) sunscreens. Physical sunscreens contain mineral ingredients—like titanium dioxide or zinc oxide—and sit on top of the skin to deflect and distribute damaging UVA and UVB rays away from the skin. These sunscreens are safer for the skin (and especially non-irritating for oily, acne-prone, and sensitive skin types), and contain no harmful chemicals.

As for how long SPF in sunscreen lasts, it all depends on the UV index for the day, your skin color, and the SPF number you use, says Dr. Jaliman. The higher the UV index is, the higher your risk of UV exposure and chance of sunburn. Because the UV index can be affected by time of year, cloud coverage, and elevation, it’s important to check it before heading outside, she advises.

Since sunscreen does not protect the skin against 100% of UV rays, it’s always best to choose one with a high SPF and also practice sun protective behavior while in the sun. Try to sit in the shade during peak hours (between 10 o’clock in the morning and 2 o’clock in the afternoon), wear hats, glasses, and clothing with UPF (ultraviolet protection factor) when outdoors, and reapply your sunscreen every two hours, recommends Dr. Zeichner.

What to look for in sunscreen

According to the American Academy of Dermatology and the Skin Cancer Foundation, you should be wearing sunscreen with an SPF of at least 30. However, Dr. Zeichner recommends choosing sunscreen with an even higher SPF. Many of us do not apply as much sunscreen as we should, and we also may not reapply, so starting out with a sunscreen with an ultra high SPF ensures the best level of protection possible.

Keep an eye out for keywords on the packaging, like waterproof, hypoallergenic, paraben-free, and noncomedogenic (read: won’t clog pores), and opt for water-resistant sunscreen if you plan to be swimming or sweating a lot, says Dr. Jaliman.

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