St. Mark's Hospital - July 08, 2019

When it comes to SPF numbers on sunscreen, bigger isn’t always better—well, not much anyway. But that hasn’t stopped manufacturers from marketing high-SPF products to consumers. The Environmental Working Group says the number of products with SPF 70 or higher has quadrupled in the past decade.

SPF, or sun protection factor, indicates how well a product protects against UVB rays, which cause sunburn. SPF 15 blocks 93 percent of UVB rays, whereas SPF 30 blocks 97 percent and SPF 50 blocks 98 percent. No sunscreen can block all rays.

So, should you buy a higher SPF product? You can, but you may be paying more for only a modest amount of extra protection. In fact, products with greater than 30 SPF may create a false sense of security and tempt you to stay in the sun longer or reapply it less often.

SPF-blocking ingredients also do not protect you from UVA rays, which can damage skin and cause wrinkling. So be sure to choose a sunscreen that’s labeled “broad spectrum.”