Bad breath can be unpleasant but it may also be more than just a nuisance. It can signal a change in the body and may even be a sign of a serious disease. The following is a list of the main causes of bad breath, some of which you may find surprising:

• Foods
  You are likely aware that certain foods can cause bad breath, onions and garlic for example. But the breakdown of food particles from some less flavorful foods can also cause odor. Foods high in protein like meat and nuts as well as dairy products are produce amino acids that bacteria along the gastrointestinal tract use for fuel. The byproduct of this is a foul smell. Eating foods that contain volatile oils, including garlic, onions, and several other vegetables and spices, causes you to emit these oils form your lungs until the food has passed through your body, meaning they can cause bad breath for as long as three days!


• Dental problems
  Poor oral hygiene can cause food particles remain in your mouth where they form a thin film called plaque. These bacteria emit hydrogen sulfide vapors, the same gas responsible for the sulfur smell in rotten eggs. Also, if you have gum disease (gingivitis or periodontitis) it can cause bad breath, regardless of your oral hygiene.


• Dry Mouth
  Saliva cleanses your mouth and without it, dead cells and bacteria can accumulate in your mouth. This happens naturally as we sleep, leading to the familiar “morning breath,” especially if you sleep with your mouth open. Other natural causes of dry mouth include aging and reduced chewing.


• Medications
  Several medications can reduce your saliva production, causing dry mouth and bad breath. Dry mouth is one of the most commonly listed side effects of medications and can occur when taking antidepressants, diuretics, antihistamines, beta blockers, chemotherapy drugs used to treat cancer, and even aspirin.


• Mouth breathing
  Day or night, breathing through your mouth can dry it out, causing bad breath. Some people breathe through their mouths naturally, while others do so because of a medical issue such as sleep apnea, snoring, or asthma.


• Respiratory tract infections
  Infections of the upper or lower respiratory tract can lead to bad breath. In addition to oral infections such as tooth and gum disease mentioned above, this may include sinus infections that cause a buildup of bacteria in the sinuses and result in post-nasal drainage into the back of your throat; throat infections such as strep throat; and even bronchitis. All of these conditions cause mucus production that can feed bacteria living along the respiratory tract.


• Chronic diseases
  Ongoing disease conditions may also cause bad breath. Chronic lung infections can cause a very foul odor to the breath, but so can several diseases that are not directly related to the respiratory tract. Some cancers can cause a distinctive breath odor. Kidney failure, which prevents the body from eliminating waste products, can cause a urine-like odor to the breath, and liver failure, which prevents the body from detoxifying chemicals, may cause a fishy odor. Gastroesophageal reflux disease (GERD), which causes stomach contents to flow up into the esophagus, can cause bad breath. Metabolic disorders such as uncontrolled diabetes can cause the breath to have a fruity smell.


• Very low carbohydrate diet
  If you don’t eat enough carbohydrates (sugars), either because you skip meals or you are on a low carb diet, your breath may take on the same fruity smell as someone with uncontrolled diabetes. In both cases, the body lacks carbohydrates to provide energy to the brain so it begins breaking down proteins and fats to make new carbs, a process which creates ketone bodies as a byproduct. The substances accumulate in the body (ketosis or ketoacidosis) and are excreted in the breath.


• Tobacco products
  Smoking dries out your mouth and causes its own unpleasant mouth odor. Both smking and chewing tobacco increase the risk of gum disease and tooth decay, which also cause bad breath.


• Alcohol
  Alcohol consumption can dry out the mouth, leading to bad breath. Also, consuming too much alcohol can make you more likely to snore or sleep with your mouth open, further drying out the mouth and causing bad morning breath.

_{Sources: Mayo Clinic, www.mayoclinic.com; U.S. News and World Report, "8 Surprising Causes of Bad Breath" By Megan Johnson, December 2, 2008.}

_{Photo: lastrandy, Flickr, Creative Commons}