What are the causes for Bad Breath
(Halitosis)?

Bad breath (halitosis) can be caused by a variety of things, including diet, medication, poor oral hygiene, and diseases or conditions such as diabetes, GERD, lactose intolerance, gum disease, and more. Treatment for bad breath depends on the cause. Causes of bad breath include the following: Diet
  • When a person does not brush or floss their teeth thoroughly, food particles that may remain in the mouth can rot and cause foul odors. In addition, food particles over time can promote the growth ofbacteria, which can also cause foul odors. The bacteria can also lead to tooth decay and gum disease.
  • Foods with strong odors also affect the air a person exhales. Foods commonly known to contribute to bad breath include onions andgarlic, exotic spices (such as curry), some cheeses, fish, and acidic beverages such as coffee. Foods are absorbed into the bloodstream and then transferred to the lungs, causing noticeable odors when exhaled. These foods may also cause stomach and gastrointestinal upset and belching, which can contribute to bad breath. In addition, certain supplements, such as fish oil capsules, can contribute to bad breath.
  • Low-carbohydrate diets may also cause what is known as "ketone breath." So-called "low carb" diets cause the body to burn fat as its energy source. The end product of making this energy is ketones, which cause a fruity acetone-like odor on the breath when exhaled.
Dry Mouth
  • Bad breath can also be caused by decreased flow of saliva, which is a vital part of the digestive process and removes odor-causing particles in the mouth. Also called xerostomia, dry mouth may be caused by medications, breathing through the mouth, or salivary gland problems.
Tobacco Products
  • In addition to causing bad breath, smoking or chewing tobacco-based products can stain teeth, irritate gum tissue, and exacerbate tooth decay.
Medical Disorders Certain medical disorders may cause bad breath:
  • gum or periodontal infection,
  • throat infection (pharyngitis or tonsillitis),
  • local infection in the respiratory tract,
  • chronic sinusitis and/or postnasal drip,
  • chronic bronchitis,
  • diabetes,
  • gastroesophageal reflux disease (GERD),
  • liver or kidney disease,
  • Sjögren's syndrome (causes xerostomia),
  • lactose intolerance.
Dentures or Dental Appliances
  • Dentures or dental appliances, such as braces, can contribute to bad breath. Most often, it is due to food particles that are not properly cleansed from the appliances. Loose-fitting dentures can contribute to sores and localized infections in the mouth, which can cause bad breath.
Morning Breath
  • Overnight, bacteria accumulate in the mouth, which can cause bad breath, commonly referred to as "morning breath." Some people breathe through their mouths at night, which can cause dry mouth and worsen morning breath.

    Source: http://www.emedicinehealth.com