Especially during summer, a daily slathering of sunscreen is essential weaponry against skin cancer—not to mention future sun spots and wrinkles. But as late-season heat waves roll in, that SPF you’ve been diligently applying might lead to suffocated pores and ruddy patches of inflammation, especially if you’re not taking the time to properly remove it each evening.

“It is not dangerous to fall asleep with SPF, but don’t be surprised if you wake up with a face full of acne!” warns Manhattan-based dermatologist Dr. Lisa Airan, M.D.