Ideally, our nighttime routine involves a warm cup of tea, a hot shower, and a good book. The reality: dozing off in front of late-night TV then dragging our bleary-eyed selves to bed. Whether the result of a few too many drinks, exhaustion, or pure laziness, we’ve all had those nights when washing our face just isn’t going to happen. But is it really that bad?

The Need-to-Know

All signs point to yes. “It’s one of the worst things we can do,” says Joel Schlessinger, M.D., a dermatologist and RealSelf contributor. Throughout the day, your makeup picks up harmful free radicals from the air. These unstable molecules break down the collagen in your skin and speed up the aging process, Schlessinger explains. Not washing them away at night gives them time to do their dirty work as you sleep.

Basically, it’s enemy No. 1 for clear, smooth skin. “There’s truth to the phrase ‘beauty sleep,’” says Whitney Bowe, M.D., a dermatologist in New York City. Sleeping in makeup traps in oil, which leads to bacteria build-up and breakouts. Removing it, on the other hand, gives your skin a clean palette for any nighttime products to soak in.

The Culprits

All types of makeup can cause damage, but some are worse than others. “Foundations and primers, especially oil based, can block pores and deter your skin from breathing,” Bowe says.

Concealer tends to aggravate acne, Schlessinger says—which is a cruel and unusual punishment, since you’re likely using it to cover up blemishes in the first place. And leaving lipstick on can result in chapped, dry lips.

Your lashes aren’t safe either. “Leaving mascara on overnight can cause eyelashes to become brittle, break easily, and even shed faster,” Schlessinger says. Eye makeup can also lead to irritation or even more serious eye infections, like conjunctivitis, if particles make their way into your eyes as you’re tossing and turning. Yuck.

What If It Happens?

Don’t beat yourself up—it doesn’t mean you’ve done irreversible damage: “Skin does have a natural resiliency to environmental stress and damage, so it will protect itself to a certain extent,” Bowe says. Just don’t make it a habit. Although one time won’t do damage, eventually premature aging will set in, Schlessinger says.

Your morning-after action plan: Wash your face twice instead of once, Bowe suggests, and apply a face mask to add back some moisture if you have time. Another good call: Wash your pillowcase before getting back in bed, since leftover makeup and bacteria will likely linger.

For an occasional quick fix, store makeup-removing wipes, like Josie Maran’s Bear Naked Wipes ($12;, on your nightstand, Bowe suggests. Just don’t rely on them every night. “They aren’t as effective as washing your face with a cleanser,” she says. Still, they may serve as a nightly reminder to head to the bathroom for a more thorough cleanse.

You can also try a cleansing “water” that remove impurities and makeup—without the need for actual H2O. Our derms recommend Dr. Brandt’s XYY Dual Fusion Water ($32; or La Roche-Posay’s Micellar Water ($19.99;