See Allergies in our Ailments section for more information. Bad breath may also be the sign of potentially more serious medical conditions such as diabetes, duodenal ulcers, hypoglycemia, kidney or liver malfunction, and respiratory disorders. The foods eaten also are a potential cause of halitosis. Certain foods, such as garlic, onions and certain spices are frequently cited as cause for a person's bad breath. Both vegetarians and those who eat large quantities of meat may develop bad breath due, in part, to the digestive process.
Digestion begins in the mouth.
Saliva has enzymes which begin the digestion process, and the type of food eaten can affect the food chemistry of the mouth. Saliva will also pick up odors from food within several hours after it has been eaten. Odors are strongest from carbohydrates - sugars, starches and cellulose, less strong from proteins, and nonexistent from fats. Bacteria in the mouth react with the decaying food and drink residue and can be the source of the foul odor. The stomach also is an area that causes bad breath problems for many people.