This past Saturday, I did something I’d never ever done before—I put my nighttime skin-care products on without first washing my face. I had cleansed and applied products in the morning and then spent the day in my living room, watching movies and knitting—no sweating and no exposure to pollutants. By the end of the day, I was exhausted and couldn’t bare to wash my face. But, I still slathered on my Dr. Naomi One Night Stand overnight mask and then hopped into bed.

The next day, the beauty editor in me couldn’t help but wonder: Is putting skin care on without cleansing first a terrible idea? According to Marisa Garshick, MD, a board-certified dermatologist in New York City, it depends.

“Some days there’s more on our face—we’ve actually intentionally put makeup on or other things like sunscreen, and we have a lot of stuff just kind of sitting on the surface of the skin. And then other times we accumulate dirt, build up, bacteria, just things from being in the environment throughout the day,” says Dr. Garshick. “And so what ends up happening is if we don’t wash our faces prior to putting other products on, those products are essentially sitting on top of whatever layer is already existing on the skin.”

If you’ve done anything that can cause build-up on the skin—like sweating or going outside in a polluted area— or if your skin is visibly dirty or covered in foundation, you definitely don’t want to layer on skin-care products without cleansing.

“Applying something that’s designed to occlude the skin or lock in moisture may also lock the bad stuff in,” says Dr. Garshick. “If something’s occlusive, then it means it’s preventing things from getting out, so all of a sudden, you’re kind of trapping anything that’s been built up on the skin. And that’s really where we get into this idea of how not washing your face at night and things like that can lead to irritation or breakouts or issues on the skin just because you’re essentially trapping all this stuff in that the skin actually doesn’t want to sit on the surface.”

In this case, the best choice is obviously to wash your face. But if that’s not an option, you’re better off foregoing the rest of your routine entirely than applying products on top of dirty skin.

If you know your skin isn’t dirty because it’s the end of a day spent in the house, or it’s first thing in the morning and you washed your face the previous night, putting products on without cleansing isn’t as problematic, but it may not be effective. Say all that’s on your face is residue from the skin care you applied 12 hours ago. “Theoretically you could put something on top of it cause it’s not necessarily a harmful ingredient that you’re now layering on top,” says Dr. Garshick. But if your face is still shiny from last night’s face oil, she says you probably want to rinse it off because “if there’s something in between where your product is and where your skin is, even if it’s that sort of a microscopic layer of buildup, um, it may impact the penetration of the ingredients that you actually want to get into the skin to do their thing.”

No matter what the circumstances are, do your best to make sure that you regularly wash your face before applying skin care. But if there’s a day when that’s not possible, it’s not the end of the world. “A one-time occurrence is not necessarily gonna make or break your skin,” says Dr. Garshick. If you generally have a hard time cleansing regularly, especially at night Dr. Garshick suggests keeping a water-free cleansing option handy like a cleansing balm or micellar water for nights like this so you can cleanse with minimal effort.

“I myself used a Simple face wipe instead of washing my face last night, so I am definitely guilty not wanting to do anything to my skin at night too,” says Dr. Garshick. “But, the act of removing buildup is very important.”

Simple Kind To Skin Cleansing Facial Wipes — $7.00

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