Understanding SPF in Sunscreen

Walk into any store to purchase sunscreen and you’ll be bombarded with all of the choices—not just in brands, but with their Sun Protection Factor (SPF) levels. Do you know what SPF means or its significance in protecting your skin?

SPF is a measure of how well a sunscreen protects your skin from the sun’s harmful ultraviolet A (UVA) or ultraviolet B (UVB) rays, which can cause sunburn and possibly lead to skin cancer. The higher the number, the higher the protection, but once you get beyond SPF 30, the difference in coverage is minimal.

For example, SPF 15 blocks 93 percent of UVB rays, SPF 30 blocks 97 percent, SPF 50 blocks 98 percent and SPF 100 blocks 99 percent. As you can see, once you get over SPF 30, you are only getting a very small jump in UVB protection.

What’s most important about sunscreen is when and how you apply it.  Here are some tips you should follow:

• Apply sunscreen about 15 to 20 minutes before going out in the sun.
• Reapply sunscreen every 90 minutes, regardless of its SPF or whether it’s waterproof.
• Be generous with the amount of sunscreen you apply and rub it in thoroughly.
• While a sunscreen with SPF 30 is suitable for the average person, if you tend to burn easily, or have delicate skin (such as with babies), using a higher SPF sunscreen is recommended.