This story originally appeared on Thisisinsider.com.
It's common knowledge that sleeping in a full face of makeup is a bad idea. But even if you wash your face, there could be trace layers of makeup left over.
That's according to Dr. Rebecca Kleinerman, a dermatologist practicing in New York City, who told INSIDER that leaving makeup on your face can interfere with the appearance of your skin.
"By leaving the makeup on your skin, a.) it clogs pores so that can lead to sebum build up, which potentially leads to more acne, and b.) it can interfere with your skin's natural ability to repair itself and exfoliate properly," she said.
Plus, in order for renewing and anti-aging products like retinoids and alpha-hydroxy acids to work, you can't have makeup on your skin.
"So you want to make sure that your makeup is fully removed at night before you go to bed," she added.
To make sure that your face is completely clean before applying any products, follow Kleinerman's advice for making sure you get all of your makeup off:
1. First, use a cleansing or makeup removing wipe to get rid of the first layer of your makeup
(preferably when you first get home from work).
2. Next, use a gentle cleanser to wash your face.
Some experts suggest using warm water to start and finishing with cool water.
"If you like a gentle cleanser that doesn't have fragrance, Cetaphil is a pretty common one," Kleinerman recommended. "CeraVe Hydrating Cleanser is also good, and I like one by a company called Rituals, which makes a cream cleanser, but that has a little fragrance so if you have sensitive skin, that's not a good option for you."
3. Finish with an alcohol-free toner to remove any residual makeup.
"If you use the toner, at the end of the cleaning ritual, and you notice there's still makeup on the cotton wipe, then you still have makeup on your skin," she said.
So to sum up: Use makeup wipes to remove makeup, cleanse your face, and then finish with a toner.
Easy enough. Now go wash your face.