Medication. Hundreds of over the counter and prescription medications list dry mouth as a potential side effect. These include antihistamines for allergies, antidepressants, heart, blood pressure, and chemotherapy medications. Dry mouth complications happen and must be dealt with. When the mouth is dry, when insufficient saliva is present to flush away food particles, bad breath thrives. Medications break down when consumed and sometimes release compounds that move through the bloodstream and release unpleasant smelling chemicals in perspiration and the breath. Taking large doses of certain vitamins or other nutritional supplements can also predispose a person to have bad breath. Good oral hygiene can help with bad breath. Brushing and flossing teeth often, several times a day if possible is a great head start. Drinking a lot of water will keep your mouth moisturized. Stimulating the production of saliva by chewing sugarless gum, or by keeping a piece of sugarless candy in the mouth, will help provide the moisture needed to wash away bacteria and food fragments.