More than 90 million people suffer from chronic halitosis or bad breath. In most cases it originates from the gums and tongue. The odor is caused by bacteria from the decay of food particles, other debris in your mouth, and poor oral hygiene. The decay and debris produce a sulfur compound that causes the unpleasant odor. Bad breath is primarily caused by poor oral hygiene, but can also can be caused by retained food particles or gum disease.

Proper brushing including brushing the tongue, cheeks, and the roof of the mouth will remove bacteria and food particles. Flossing removes accumulated bacteria, plaque and food that may be trapped between teeth. Mouth rinses are effective in temporary relief of bad breath. Consult your dentist and/or physician if the condition persists.Bad breath also may occur in people who have a medical infection, gum disease, diabetes, kidney failure, or a liver malfunction. Xerostomia (dry mouth) and tobacco also contribute to this problem. Cancer patients who undergo radiation therapy may experience dry mouth.

Even stress, dieting, snoring, age and hormonal changes can have an effect on your breath. An odor that comes from the back of your tongue may indicate post-nasal drip. This is where the mucus secretion, which comes from the nose and moves down your throat, gets stuck on the tongue and causes an odor. Bad breath originating in the stomach, however, is considered to be extremely rare. Saliva is the key ingredient in your mouth that helps keep the odor under control because it helps wash away food particles and bacteria, the primary cause of bad breath. When you sleep, however, salivary glands slow down the production of saliva allowing the bacteria to grow inside the mouth.

To alleviate "morning mouth," brush your teeth and eat a morning meal. Morning mouth also is associated with hunger or fasting. Those who skip breakfast, beware because the odor may reappear even if you've brushed your teeth.

Researchers have for many years tried to develop scientific ways to quantify different degrees of halitosis. It's easy to understand how the appraisal of halitosis by smelling might vary from one individual tester to another, but researches have also had to cope with the fact that any one tester's evaluation of a person's halitosis will deviate too. This variance depends on factors such as hunger, menstrual cycle, head positioning, and the number of consecutive times the tester has been exposed to an odor.

Several scientific apparatuses have been used to help to quantify the degree of a person's halitosis. These include gas chromatographs, sulfide meters (Halimeters), and chemiluminescence detectors.