If I ever get skin cancer, I’ll blame it on the time I burned myself so badly I thought my face was going to peel off. Hiking high up on Mount Rainier, in Washington, where the snow reflects light onto one’s face from all directions and the frigid air keeps skin numb to the injury, I put on SPF 100 at dawn and didn’t think about it again. The next morning I was so inflamed it hurt to smile.
To understand why people like me make such stupid and consequential mistakes—one in five of us will get skin cancer, despite most cases being preventable—last year a trio of dermatologists at Northwestern University asked its patients to take a quiz about sunscreen. The doctors, who spend much of their careers sampling and extracting what they call “suspicious lesions” from people’s faces (among other places), needed to know why we’re not better at preventing cancers. Because even though cancer is often listed among the most terrifying words in the English language, and one of the most common types (skin cancer) can be prevented through the simple measure of avoiding excessive ultraviolet radiation, these cancer rates aren’t falling.
A big part of that discrepancy, the dermatologists found, seems to come down to misinformation about how to use sunscreen. The fact that the quiz takers were patients at a dermatology clinic means they cared at least somewhat about skin to begin with. Even still, they knew little about how to use the tool that keeps that skin from breaking down, wrinkling, and mutating. The doctors reported in JAMA Dermatology that fewer than half of people could define SPF (sun protection factor). Fewer still knew how to use the number.