Breath odor is the scent of the air you breathe out of your mouth. Unpleasant, distinctive, or offensive breath odor is commonly called bad breath.

Some disorders will produce specific, characteristic odors to the breath.

A fruity odor to the breath occurs as the body attempts to get rid of excess acetone through the breathing. This is a characteristic sign of ketoacidosis, which may occur in diabetes, and is a potentially life-threatening condition.

A fecal odor to the breath (the breath smells like feces) can occur with prolonged vomiting, especially when there is a bowel obstruction. It may also occur temporarily if a person has a nasogastric tube (a tube placed through the nose or mouth to the stomach to drain the stomach contents) in place.

The breath may have an ammonia-like odor (also described as urine-like or "fishy") in people with chronic kidney failure.

If previously normal breath turns into halitosis, causes could include:

• Food or beverages consumed (such as cabbage, garlic, raw onions, or coffee)
• Vitamin supplements (especially in large doses)
• Poor dental hygiene
• Dentures
• Cavities
• Tobacco smoking
• Alcoholism
• Throat infection
• Sinusitis
• Lung infection
• Gum disease (gingivitis, gingivostomatitis)
• Abscessed tooth
• Impacted tooth
• Foreign body in the nose (usually in children)
  • Often (but not always) there is a white, yellowish, or bloody discharge from one nostril
• Drugs
  • Paraldehyde
  • Triamterene and inhaled anesthetics
  • Insulin - injection

• Acute necrotizing ulcerative gingivitis
• Acute necrotizing ulcerative mucositis
• Acute renal failure
• Bowel obstruction (can cause breath to smell like feces)
• Bronchiectasis
• Chronic renal failure (can cause breath to smell like ammonia)
• Diabetes (fruity or sweet chemical smell with ketoacidosis)
• Esophageal cancer
• Gastric carcinoma
• Gastrojejunocolic fistula (fruity-smelling breath)
• Hepatic encephalopathy
• Diabetic ketoacidosis
• Lung abscess
• Ozena, or atrophic rhinitis
• Periodontal disease
• Pharyngitis
• Zenker's diverticulum

Use proper dental hygiene (especially flossing), and remember that mouthwashes are not effective in treating the underlying problem.

Fresh parsley or a strong mint are often effective ways to fight temporary bad breath. Avoid smoking. Otherwise, follow prescribed therapy to treat the underlying cause.