What is SPF?

Sun Protection Factor, or SPF, measures the length of time a sunscreen will protect your skin from burning. Simply speaking, the higher the number of the SPF, the longer you can stay in the sun without turning into a tomato.

Explaining the SPF formula

Minutes it takes you to get a sunburn x SPF number =
minutes of sun protection.

For instance, a 30 minute burn threshold multiplied by an SPF 15 sunscreen would equal 450 minutes (or 7.5 hours) of burn protection. For maximum protection, apply sunscreen 15 to 30 minutes before going outside, and reapply every two hours and right after swimming. 

For instance, if it takes 20 minutes in the sun without protection for your skin to redden, an SPF 15 sunscreen theoretically prevents burning 15 times longer—about 5 hours. To maintain this level of protection, the Skin Cancer Foundation recommends reapplying sunscreen every two hours and right after swimming.

It’s important to note, however, that sunscreens will not shield you from all of the sun’s harmful rays. The sun emits two types of rays: UVA (Ultraviolet-A) and UVB (Ultraviolet-B).

  • UVA, while less likely to cause sunburn, penetrates the skin deeply and is the chief culprit behind wrinkling, leathering and other aspects of what has become known as “photoaging”. Recent studies also suggest that UVA may induce some skin cancers—a frightening thought considering sunscreens don't block out all of these these long-wave solar rays.
  • UVB is considered the more harmful of the two. These short-wave solar rays are responsible for causing sunburn and have been directly linked to various forms of skin cancer. Fortunately, sunscreens, if used properly and frequently, provide ample protection against UVB.

So what can you do to protect your little one’s sensitive skin from the sun? The best defense remains a combination of SPF 15 sunscreen (SPF 30 is recommended for those with very fair skin); sun-protective clothing; sunglasses; plenty of shade; and avoiding direct exposure to the sun between 10 a.m. and 4 p.m., when UVB levels are at their most dangerous.

And remember: Sunscreens are not intended to increase the amount of time you spend in the sun but to increase protection during unavoidable exposure. You can still have fun in the sun; just make sure you’re covered first.