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.

• Breath odor persists and there is not an obvious cause (such as smoking or eating odor-causing foods).
• You have breath odor and signs of a respiratory infection, such as documented fever, cough, or facial pain with nasal discharge

The medical history will be obtained, and a physical examination performed.

Medical history questions documenting breath odor in detail may include:

• Is there a specific odor?
• Is there a fishy smell?
• Does the breath smell like ammonia or urine?
• Does the breath smell like fruit or is there a sweet-chemical smell?
• Does the breath smell like feces?
• Does the breath smell like alcohol?
• Has the person recently eaten a spicy meal, garlic, cabbage, or other "odorous" food?
• Does the person take vitamin supplements?
• Does the person smoke?
• Does good oral hygiene improve the odor?
• What home care measures have been tried? How effective are they?
• Is there a recent sore throat, sinus infection, tooth abscess, or other illness?
• What other symptoms are also present?

The physical examination will include a thorough examination of the mouth and the nose. A throat culture may be taken if the patient has a sore throat or mouth sores.

In rare cases, diagnostic tests that may be performed include:

• Endoscopy (EGD)
• X-ray of the abdomen
• X-ray of the chest
• Blood tests to screen for diabetes or renal failure

Antibiotics may be prescribed for some conditions. For an object in the nose, the doctor will use an instrument to remove it.