As pointed out in this weekend’s Wall Street Journal, this is the burning question for those of us in the northern hemisphere as we enjoy our brightest days of the year. According to The Numbers columnist Jo Craven McGinty, the answers are:
- At least 2 milligrams per square centimeter—about one-fifth the depth of a piece of paper. Although this seems very thin, most people only put on about half that amount, so you’d best apply your sunscreen twice.
- Go for at least an SPF of 50. However, do not sweat it if all you have on hand is SPF 30, or the level 50 costs more than you care to pay—the difference is minor as you can see in the graph I made by fitting the FDA data WSJ
provided to a curve (using Design-Expert® software).
It seems to me it would be best to stay out of the sun as much as possible, and, when you do, cover up, but seek the advice of your physician or other qualified health provider, such as a dermatologist. Be careful out there!
PS. McGinty detailed a study that found a significant advantage to increasing SPF from 50 to 100. It being done via a randomized split on 199 snow skiers bodes well. However, the research was sponsored by a sunscreen maker. An independent, contrary view of 100 SPF pros and cons is laid out here.