You'll hardly find a person alive who hasn't experienced it: dry mouth at night, followed by a terrible case of bad breath in the morning. This cause of halitosis is very difficult to prevent, but never fear! Rather than avoiding it in the first place, it's much easier to simply treat this condition after the fact, using a specialty breath freshener.
During the day, any number of things can cause a dry palate. According to the National Institute of Dental and Craniofacial Research, these include mouth breathing, medications (some prescriptions are notorious for leaving you with cottonmouth), anxiety, exercise, smoking, drinking or - though it is rare - a genetic condition called Sjogren's syndrome that causes the salivary and tear glands to dry up.
Dry mouth at night, on the other hand, has one primary cause: sleeping with the mouth open. Most people, particularly those who snooze on their backs, periodically have their mouths fall open during the night. Even 15 minutes in this position can give oral tissue enough time to dry out and bacteria to multiply.
The result is a bad case of morning breath, an odor everyone is familiar with.
Preventing dry mouth at night is tough, for the simple reason that you can't control your body when you're unconscious. Since tying your jaw shut isn't the best idea - what happens if your nose gets stuffed up? - it's better to wait until morning and then immediately rinse with a specialty, alcohol-free mouthrinse.
The only real prevention for morning breath are probiotics, which encourage "good" bacteria to crowd out the varieties that give off odors. These can be taken every day, usually in the evening, just before bedtime.