Protecting yourself from the sun seems pretty straightforward: Just smear on some sunscreen and go. But judging from a new study, you’re probably doing it wrong. In a survey of 423 adults at New York City’s Memorial Sloan-Kettering Cancer Center, fewer than a third were aware that sunscreen should be applied 30 minutes before going outside (it takes that long for it to soak into skin and create a shield). And a mere 18 percent knew that you need a full ounce of the stuff, about two tablespoons, to adequately cover your bathing-suited body. These misunderstandings aren’t minor, says lead researcher Steven Q. Wang, MD—they mean you’re not properly shielded from the sun’s damaging rays.
Plus: Check out more summer safety tips.