Causes of Halitosis - Bad Breath - Breath Odor

The causes of bad breath are numerous. They include:

Food.
The breakdown of food particles in and around your teeth can cause a foul odor. Eating foods containing volatile oils is another source of bad breath. Onions and garlic are the best-known examples, but other vegetables and spices also can cause bad breath. After these foods are digested and the pungent oils are absorbed into your bloodstream, they're carried to your lungs and are given off in your breath until the food is eliminated from your body. Onions and garlic can cause bad breath for as long as 72 hours after you've eaten them.
Dental problems. Poor dental hygiene and periodontal disease can be a source of bad breath. If you don't brush and floss daily, food particles remain in your mouth, collecting bacteria and emitting hydrogen sulfide vapors. A colorless, sticky film of bacteria (plaque) forms on your teeth.

If not brushed away, plaque can irritate your gums (gingivitis) and cause tooth decay. Eventually, plaque-filled pockets can form between your teeth and gums (periodontitis), worsening this problem — and your breath. Dentures that aren't cleaned regularly or don't fit properly also can harbor odor-causing bacteria and food particles.

Dry mouth.
Saliva helps cleanse and moisten your mouth. A dry mouth enables dead cells to accumulate on your tongue, gums and cheeks. These cells then decompose and cause odor. Dry mouth naturally occurs during sleep. It's what causes "morning breath." Dry mouth is even more of a problem if you sleep with your mouth open. Some medications as well as smoking can lead to a chronic dry mouth, as can a problem with your salivary glands.

Diseases.
Chronic lung infections and lung abscesses can produce very foul-smelling breath. Other illnesses, such as some cancers and certain metabolic disorders, can cause a distinctive breath odor. Kidney failure can cause a urine-like odor, and liver failure may cause an odor described as "fishy." People with uncontrolled diabetes often have a fruity breath odor. Chronic reflux of stomach acids from your stomach (gastroesophageal reflux disease, or GERD) also has been associated with bad breath.

Mouth, nose and throat conditions. Bad breath is also associated with sinus infections because nasal discharge from your sinuses into the back of your throat can cause mouth odor. A child with bad breath may have a foreign object lodged in his or her nose. A bean or small item stuck in the nose can cause persistent nasal discharge and a foul odor. Throat infections can cause bad breath until they clear. Bronchitis and other upper respiratory infections in which you cough up odorous sputum are other sources of bad breath.

Tobacco products.
Smoking dries out your mouth and causes its own unpleasant mouth odor. Tobacco users are also more likely to have periodontal disease, an additional source of bad breath.

Severe dieting.
Dieters may develop unpleasant "fruity" breath from ketoacidosis, the breakdown of chemicals during fasting.