I recently stayed at a friend's place during a vacation, and she was amused by how long my evening skin-care regimen took. Not only do I wash my face with a cleanser, but I remove my makeup with a wipe, then follow up with a chorus line of lotions and potions to keep my skin looking A+. When I woke up the next morning and realized she was still wearing her makeup from the night before, I understood why she had been laughing. She, like a ton of other women, doesn't always wash her face before bed. And the insane thing is that she knows it's bad for her skin . She just shrugs her shoulders and moves on.It's no wonder that so many women are skipping their evening cleansing. Celebrities like Kim Kardashian have been open about their nocturnal makeup-wearing habits. But we're here to reiterate that even if you have a crystal-clear complexion, failing to properly cleanse before you snooze is not just bad for your skin — it's horrible. "[Sleeping with makeup on] clogs your pores, and that buildup ultimately prevents other beauty products from penetrating the skin," says dermatologist Mona Gohara, MD . So even if you're layering a fancy night cream over your old makeup to assuage your non-cleansing guilt, you're not even getting the benefits of said cream. Dr. Gohara says: "It also precludes the skin's natural exfoliation process. We shed 50 million skin cells a day. If there's makeup on, they won't be liberated as freely, resulting in a gray, lackluster appearance."