Don’t Get Burned: Know the Facts on SPF

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Just one sunburn is enough to convince most of us that it’s important to use sunscreen. But knowing what sun protection factor (SPF) to buy isn’t always so clear-cut.

The SPF tells you how well a sunscreen filters out damaging ultraviolet B (UVB) rays, the rays from the sun that cause sunburn and can lead to skin cancer. An SPF 15 sunscreen filters out about 93 percent of incoming rays to protect your skin. SPF 30 keeps out 97 percent of damaging rays, and SPF 50 keeps out 98 percent. 

The American Academy of Dermatology recommends that people use SPF 30 or SPF 50 sunscreen when spending time outdoors. A higher SPF is particularly important for people with a history of skin cancer and those who have light skin. 

Sunscreen can definitely help to prevent skin cancer, says Brent Kirkland, MD, Dermatologists of Southwest Ohio. “But it needs to be applied correctly. You need to apply sunscreen every two hours and you need to use an adequate amount. As dermatologists, we recommend applying one ounce (about two tablespoons) of sunscreen to all exposed areas of the body.”

He notes that a high-number SPF does not allow you to spend additional time outdoors without reapplying your sunscreen. If you’re sweating, swimming or toweling off, you should apply sunscreen more frequently. 

You need to apply sunscreen every two hours and you need to use an adequate amount.

Why SPF is Not Enough

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The sun not only hits us with UVB rays, but also with ultraviolet A (UVA) rays. These rays accelerate skin aging and can cause skin cancer. The SPF in sunscreen works to filter UVB rays but not UVA rays.

So, it’s important to find a sunscreen that blocks both types of rays. Look for sun protection products labeled “broad spectrum,” “multi-spectrum” or “UVA/UVB protection.” Waterproof or water-resistant sunscreens also add to your protection.

Pay attention to how old your sunscreen is. Most sunscreens are good for three years. Check for an expiration date, or mark the bottle with your date of purchase. Toss it out if it has expired, recommends Dr. Kirkland. 

“If you’re using enough, you should finish an entire bottle of sunscreen before the expiration date,” he says.

Because no sunscreen can block 100 percent of the sun’s rays, and most of us fall short of putting on enough sunscreen with enough frequency, dermatologists recommend additional ways to protect your skin:

  • Stay in the shade as much as possible between 10 a.m. and 2 p.m.
  • Wear a hat, sunglasses and clothing that covers your skin as much as possible.
  • Be aware of more intense effects of the sun near water, snow and sand — and protect yourself accordingly.
  • Avoid tanning beds, whose ultraviolet light can cause skin cancer and wrinkling.
  • See a doctor if you notice abnormal-looking spots on your skin or have spots that itch or bleed. 
Small Steps: Print It and Go.
Take this handy chart of what screenings you should get when to discuss at your next doctor’s appointment.