SPF: How High Should I Buy?

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I often get asked by my patients what Sun Protection Factor (SPF) they should be using and whether the higher SPF (SPF 50+) are really that much better than a SPF 30. The simple answer is to aim for a broad-spectrum sunscreen with at least a SPF of 30. To break it down:

  • SPF 15 blocks 93% of ultraviolet B rays (UVB)
  • SPF 30 blocks 97% of UVB
  • SPF 50 blocks 98% of UVB

So, there’s not a huge quantifiable difference between SPF 30 and SPF 50. However, in the real world, we often are not applying sunscreen in a perfect scenario. For instance, most of us only apply about half of the recommended amount of sunscreen to our skin, and in addition to that, sweat, water and even the sun’s rays break down the sunscreen we have applied. So, there is some thought that a higher SPF may make up for some of those human errors.

The downside of a higher SPF is that it can often give a false sense of security that we are protected better and for longer. It’s important to remember that a SPF 100 will not protect you any longer than an SPF 30; both need to be reapplied every 2 hours or immediately after swimming or sweating.

My advice is to be using a sunscreen that is:

  • Broad-spectrum (protects against both UVB and UVA light). This should be indicated on the bottle.
  • Water-resistant if swimming/sweating.
  • SPF 30 or higher

And remember, the best type of sunscreen is the one that you’ll actually use over and over again!

Dr. Healy

how to select sunscreen


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