It's something no one wants to wake up to: a dry mouth and throat. If you've ever slept with your mouth open all night, you know that it can leave your palate so dry that it is difficult to talk or swallow. Likewise, dry mouth at night usually leads to seriously bad breath, which is why using a specialty breath freshening rinse is usually a good idea.
Plenty of things cause dry mouth. For one thing, anxiety, stress or outright fright can parch your tongue faster than you'd think. As Michael Caine says in one of his earliest movies, the 1964 film Zulu, "it's fear dries the mouth, isn't it? When a man's as thirsty as this."
Speaking of thirst, needing a drink of water is another prime cause of dry mouth. Think of wandering through the desert looking for an oasis, and you'll get the idea. (While we're mentioning movies, one of the most memorable lines from 1972's Chato's Land comes from Charles Bronson: "All we got here is a handful of nothing... Dirt and dry mouths."
For whatever reason, dry mouth at night just doesn't seem to come up in film. Maybe it doesn't have the same cachet. Still, it can be a serious problem. If you sleep with your mouth open repeatedly, you may get xerostomia, or chronic bad breath. The National Institute of Dental and Craniofacial Research states that can leave you with canker sores, cracked lips and halitosis, among other nasty things.
The National Institutes of Health adds that dry mouth at night is a natural part of growing older, but that doesn't mean you have to take it lying down. Instead, try rinsing at night and in the morning with an oxygenating, mouth-moistening specialty rinse.