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Duke Medicine: SPF - How high should you go?

Posted July 12, 2010
Updated July 13, 2010

Today’s sunscreens tout Sun Protection Factors (SPFs) as high as 100 in their quest to block those ultraviolet B rays that cause sunburn.

But is an SPF rating of 100 twice as good as a 50? Not necessarily, says Kelly Nelson, M.D., a dermatologist at Duke. “SPF is a measure of the time it takes an individual to burn in the sun if they were not wearing sunscreen. Higher SPFs block slightly more UVB rays, but none offers 100 percent protection.”

Regardless of which sunscreen product and SPF you choose, Nelson recommends:

  • Remembering that there’s no such thing as a “safe tan.” A tan is a visual sign that your skin has had damage to its DNA.
  • Making sunscreen part of your daily morning routine. Use SPF 15 or 30 on your face, ears, neck, upper chest and upper arms every day. Even the sun exposure you see from walking to work and to your mailbox adds up over time.
  • Applying at least an SPF 30 liberally to all sun-exposed areas when you know you’ll be outdoors. Don’t skimp. Full body application should require two fluid ounces, the volume of a shot glass. If used properly, a typical tube of sunscreen should not last long.
  • Applying an SPF 75 too thinly makes it, in effect, an SPF 30. That’s when higher SPF sunscreens become helpful. Even with lighter-than-ideal application, the skin still sees some SPF protection.

Get more summer safety tips by reading the full article from Duke Medicine.


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  • finicula Jul 14, 2010

    Health Tip: Stay inside or walk with an oversize umbrella Hope this was helpful.

  • missparrothead Jul 13, 2010

    Guess I can never set foot on the beach again. Even w/SPF 50 and clear zinc oxide on my face applied frequently, I tan.

  • days4 Jul 13, 2010

    Arbonne sunscreen is the best that I have used.

  • thefensk Jul 13, 2010

    I read something a while back that applying sunscreen, letting it soak a short while, then applying it again, would increase its effectiveness quite a bit, like more than double. I'll have to see if I can find that citation.