Bad breath can have a number of causes, including diet, side effects from medication, and in some very rare cases, a problem with the parotid (salivary) gland. For most people, though, bad breath is caused by having a dry mouth or otherwise having low saliva production.
Saliva, which is antibacterial and antimicrobial, has an important function in the mouth, preventing decay, and shielding teeth and gums from food and drinks. When your mouth is not producing enough saliva, bacteria accumulates, which leads to bad breath. This is the reason you’ll notice bad breath most when you haven’t eaten in awhile or when you first wake up, if you often sleep with your mouth open.
The good news is that getting your salivary glands working is pretty easy—just have something to eat or drink. If you tend to skip meals, try eating more often and see if the issue clears up. Or try sucking on fruit-flavored Life Savers or lemon drops between meals. The flavor and smell will get you salivating and get the antibacterial magic of saliva working for you.