To Screen or Not To Screen
The decision to wear sunscreen or not is simple: Studies have shown that regular sunscreen use prevents skin photoaging better than any anti-aging creme. So, if you’d prefer to have youthful-looking skin as you age, instead of something resembling alligator hide, apply sunscreen daily. That said, though, nothing’s ever completely simple.
Sunscreens are a good example.
Choosing a safe, effective sunscreen is not as easy as you might think. First, there’s the issue of SPF. Sun Protection Factor numbers are supposed to inform you about the level of a product’s protection against sunburning. Take the example of a fair-skinned person who would burn after 10 minutes exposure to midday summer sun. After applying SPF 15, she should be able to stay in the sun for 150 minutes, or 15 times longer then she could without protection. Logic suggests that wearing factor 30 should provide 300 minutes of protection. But this is not the case.
SPF 30 does not provide twice as much protection as SPF 15. To put it another way: SPF 15 filters 92% of UVB rays, while SPF 30 filters about 97%, and SPF 50 filters just 98%. As you can see, beyond SPF 30, the additional sun protection with increasing SPF values is negligible. So products labeled SPF 70 or higher are all but meaningless. The key to success is to apply generously and to reapply often. Still confused? Check back next week. I’ll continue exploring the surprisingly complex issue of choosing the right sunscreen for you and your family.
Gilbert E, Pirot F, Bertholle V, Roussel L, Falson F, Padois K. Commonly used UV filter toxicity on biological functions: review of last decade studies. Int J Cosmet Sci. 2013 Jun;35(3):208-19. doi: 10.1111/ics.12030. Epub 2013 Jan 15.
Levi K. UV damage and sun care: Deciphering mechanics of skin to develop next generation therapies. J Mech Behav Biomed Mater. 2013 Feb 24. pii: S1751-6161(13)00064-7. doi: 10.1016/j.jmbbm.2013.02.008. [Epub ahead of print]