Though it may not always seem like it, the mouth's saliva performs a number of critical functions, one of which is keeping bad breath at bay. A dry mouth is a common, and commonly overlooked cause of halitosis, as a popular children's book explains.
In the slim volume Why Do I Burp?: Diet and Digestion, author Isabel Thomas breaks down just how saliva breaks down food. She notes that the moisture made by our salivary glands is full of enzymes, which are proteins that increase the rate of certain chemical reactions.
Thomas writes that different enzymes break down different types of food. Human salivary enzymes are pretty powerful, though not as powerful as those of the tarantula, which liquefy the insides of their prey, she adds.
Enzymes also keep oral bacteria from growing out of control. The mouth naturally contains hundreds of different strains of microbes. Some of these flora prefer a dry environment. These are call anaerobic bacteria, and when the moth dries out, they can multiply and release a bad odor.
The author recommends drinking plenty of water to avoid this smelly situation. The American Dental Association suggests the same, noting that some drugstores even sell artificial saliva.
Individuals with dry mouth-caused halitosis may also periodically rinse with a specialty breath freshener.