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Why do we drool in our sleep?

Internist Dr. Keri Peterson of Women's Health magazine answers embarrassing health issues like excessive sweating, drooling and bad breath.

We're sure you never drool in your sleep. But if your ... friend ... ever does, Women's Health magazine contributor Dr. Keri Peterson has some helpful advice. Peterson, a board-certified internist, appeared on TODAY this morning to tell us some reasons why this might be happening, and what you can do to knock it off.

"When you sleep, your muscles relax, your mouth falls open, and if you're lying on your side, it's gonna leak out," explains Peterson, adding this fun fact: We make a liter of saliva a day.

"Also, if you have sinus problems, or allergies, and you tend to mouth-breathe, you're gonna be more likely to have this happen to you," she continues.

To keep yourself from drooling all over your pillow -- try sleeping on your back, Peterson advises. Watch the video for more on this, plus answers to more embarrassing health questions.

Got an embarrassing health question of your own? Ask us in a comment -- a writer for The Body Odd may answer it in an upcoming post.

Follow msnbc.com health writer on Twitter: @melissadahl.