Is a frequent or persistent unpleasant odor to the breath.
Halitosis most often results from fermentation of food particles by anaerobic gram-negative bacteria in the mouth, producing volatile sulfur compounds, such as hydrogen sulfide and methyl mercaptan. Causative bacteria may be present in areas of gingival or periodontal disease, particularly when ulceration or necrosis is present.

Treatment
1. Investigate and manage possible systemic (non-oral) source if organoleptic method detects malodor from both mouth and nose.
2. Improve oral hygiene by professional and patient administered tooth cleaning.
3. Regular atraumatic tongue cleaning.
4. Regular use of antimicrobial toothpastes and mouthwashes, such as:
- chlorhexidine gluconate,
- oil-water rinse, or
- triclosan/co-polymer/sodium fluoride toothpaste.

The Merck Manual. Professional version. Halitosis. Internet. Accessed on July 16, 2016.