Halitosis describes any breath odor that's unpleasant, disagreeable, or offensive.

Medical cause:

- Bowel obstruction
- Bronchiectasis
- Common cold
- Esophageal cancer
- Gastric cancer
- Gastrocolic fistula
- Gingivitis
- Hepatic encephalopathy
- Ketoacidosis
- Lung abscess
- Necrotizing ulcerative mucositis (acute)
- Ozena
- Periodontal disease
- Pharyngitis (gangrenous)
- Renal failure (chronic)
- Sinusitis
- Zenker’s diverticulum