Bad Breath Causes

By Mayo Clinic staff

Halitosis

Most bad breath originates in your mouth. 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 certain 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 foods are eliminated from your body.
• 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 that can emit chemicals, such as hydrogen sulfide — the same compound that gives rotten eggs their characteristic smell. A colorless, sticky film of bacteria (plaque) forms on your teeth and 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. The microscopic uneven surface of the tongue also can trap bacteria that produce odors. And dentures that aren't cleaned regularly or don't fit properly can harbor odor-causing bacteria and food particles.
• Dry mouth. Saliva helps cleanse your mouth, removing particles that may cause bad odors. A condition called dry mouth (xerostomia) can contribute to bad breath because production of saliva is decreased. Dry mouth naturally occurs during sleep, leading to morning breath. Dry mouth is even more of a problem if you sleep with your mouth open. Some medications can lead to a chronic dry mouth, as can a problem with your salivary glands.
• Diseases. In about 10 percent of bad breath cases, the bad odors do not come from the mouth (extra-oral halitosis). For example, illnesses, such as some cancers and metabolic disorders, can cause a distinctive breath odor as a result of chemicals they produce. Diabetes and kidney or liver failure can lead to a fishy smell. Uncontrolled diabetes can also cause a fruity breath odor from chemicals called ketones. And chronic reflux of stomach acids (gastroesophageal reflux disease, or GERD) has been associated with bad breath. In addition, some medications — such as those used to treat high blood pressure, psychiatric conditions, or urinary problems — can indirectly produce bad breath by contributing to dry mouth. Other medications may be broken down in the body to release chemicals that can be carried on your breath.
• Mouth, nose and throat conditions. Another source of bad breath is the nasal passages. For example, bad breath is associated with sinus infections because nasal discharge that drips from your sinuses into the back of your throat (postnasal drip) can cause mouth odor. Sometimes bad breath can be traced to upper and lower respiratory infections, or ulcers in the respiratory system. And malformations of the oral-nasal cavity, such as cleft palate, can lead to bad breath because they provide ideal environments for bacteria to multiply without being disturbed. Bad breath can occasionally stem from small stones that form in the tonsils. These stones can be covered with bacteria that produce odorous chemicals. Bad breath in young children is often traced to a foreign body, such as a toy or piece of food, lodged in a nostril.
• 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.