So, it's not that acids are evil, point blank. It's just bad when people overdo it, she says. "I see tons of people overdoing retinols, overdoing glycolic, and then, they're going to have trouble, like dermatitis and other issues," she says. Luckily, her Rx is pretty simple for those who want to use acids safely and effectively. She instructs her patients to stick to one acid-packed product per day — ideally alternating a nightly glycolic and retinol — and to keep everything else gentle. Before vacations or extended periods of sun exposure, take yourself off all acids a full week before you hit the beach, which allows your skin to better protect itself. Oh, and always reapply your SPF. Have we said that already?