During the day, your skin is working to protect itself from things like sun, wind, and pollution. Skin is at a higher pH at this time, and it produces more oil, explains New York City dermatologist Jeanette Graf, MD. "When you sleep, your skin changes -- it goes into renewal mode," she says. There's more blood circulation and less oil production while it repairs all the damage it incurred during the day. On a cellular level, your skin needs sleep to recharge.
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