Bad Breath

Bad breath is a familiar case to many people. Some studies have suggested that bad breath may rank only behind dental cavities and gum disease as the most frequent reasons for visits to the dentist.

Causes

The root cause behind bad breath can range from banal, such as poor oral hygiene after meals to potentially life-threatening complications from diabetes and kidney failure.
The food you eat can affect your breath. If you eat foods with strong odors, such as garlic or onions, the smells will accompany your breath. As your digestive system breaks down food, it enters your bloodstream. Pungent oils in garlic and onions eventually enter your lungs and cause bad breath. Brushing your teeth, eating a mint or using mouthwash covers the smell, but it will not go away completely until the food has left your body.

Food particles can also remain in your mouth if you do not brush or floss daily. These particles collect between the teeth and encourage the growth of bacteria, which builds up in the mouth and causes bad breath.

Smoking and chewing tobacco can also lead to mouth odor and bad breath. In addition to their own smells, tobacco particles collect in your teeth and lead to bacteria growth in the same way that food does. Furthermore, smokers and chewers are more likely to develop gum disease, a symptom of which is bad breath.
Saliva helps cleanse the mouth and wash away food particles and bacteria. However, everyone produces less saliva while asleep, which leads to dry mouth and the dreaded "morning breath." It is worse for those who sleep with their mouths open.

In the condition called diabetic ketoacidosis, the body cannot properly break down and use glucose as an energy source, so it opts to break down body fat instead. As a byproduct of doing this, the body produces ketones. These can result in sweet, fruity breath if the disease is not addressed and the chemicals continue to build up in the blood and urine. Although it may sound more pleasant than conventional bad breath, diabetic ketoacidosis can become a serious problem if unaddressed because ketones are poisonous at high levels.
Late-stage liver failure can also cause bad breath. Also known as "Fetor hepaticus," the sweet, musty aroma is caused by dimethyl sulfide, not ketones. Because of this symptom, breath analysis could potentially be used as a diagnostic tool for detecting liver pathologies.