It’s summertime, and Daylight Saving Time, and that probably means more time spent out in the sun. While there are plenty of health benefits for getting outside and participating in fun, summer activities, you probably are also concerned about too much exposure to the sun’s harmful UV rays. Slathering on sunscreen has become a way of life, but we live in a ‘super-size me’ culture that often believes, ‘if some is good, more must be better.’ When it comes to SPF, how much is enough? And just what exactly is ‘SPF’ anyway?
SPF is an acronym for the phrase, "sun protection factor," and it is reported as a numerical value on sunscreen product labels to indicate the level of protection the product provides against ultraviolet light. The higher the SPF number, the greater the level of protection, based on a scientific measure of how how much long it takes for enough UVB to penetrate through a sunscreen and cause sunburn, compared to how fast a sunburn would occur without sunscreen. In layman’s terms, and SPF-15 sunscreen should keep you from burning for 15 times longer than if you went out in the sun without sunscreen, and an SPF-30 would provide protection for 30 times longer.
The problem is, to be effective, sunscreen needs to be reapplied every two hours (more frequently if you are swimming or sweating a lot). If your unprotected skin would normally burn in 10 minutes, an SPF-15 sunscreen would protection you for 150 minutes, or two and a half hours. An SPF-30 would protect you for 300 minutes or five hours, but in both cases you still have to reapply after two hours. An SPF 15 sunscreen blocks 93 percent of UVB radiation, an SPF 30 sunscreen blocks nearly 97 percent, and at SPF 50 the protection goes up to 98 percent. Above that the increase in UVB protection is minimal, according to the Skin Cancer Foundation.
Whichever level of SPF protection you choose, the important thing is to use it as directed.