Here’s everything you need to know about sunscreen: Wear it. But if it were that simple, you’d have no wrinkles, no spots, and your skin exams would be a triumph. You would never have felt the flames of a sunburn as they licked your body. But you are human and you are imperfect. You forget. You find sunscreen sticky, you don’t apply enough, you don’t re-apply sufficiently. Also you forget. You tell yourself you’re just running out for coffee, walking the dog, dashing from front door to car door—and that can’t possibly count. Bless.

“Sun damage is all about those incidental exposures,” says Dr. Heather Rogers, a board-certified dermatologist based in Seattle, where it rains nearly half the year. And still she’s covered in the stuff.