Halitosis. A foul odor emanating from the mouth. It’s not a medical emergency, of course, but some 25 to 30 percent of the world’s population suffer with this distressing problem. The origins of bad breath are not mysterious: dental cavities, gum disease, poor oral hygiene, coated tongue (a white or yellow coating on the tongue, usually due to inflammation) are among the most common. Hundreds of bacteria live in our mouths and some of them—on the tongue or below the gumline or in pockets created by gum disease between gums and teeth, for example—create sulfurous smells. Other causes may include malnutrition (fat breakdown gives your breath a fruity odor), uncontrolled diabetes, and dry mouth (saliva has an antimicrobial effect). Infections such as sore throat or sinusitis, or intestinal disorders, such as heartburn, ulcers, and lactose intolerance, also result in bad breath. Bad breath can be int...