People often complain of a persistent bad breath without realizing that the cause is usually quite simple.

1) Dental plaque- the most common reason for bad breath. Plaque accumulates daily between and around teeth. Daily flossing, not just brushing, is recommended. Tongue cleaning is important. A regular dental checkup at least once every six months is advised by the American Dental Association. In addition, a checkup with a Periodontist (gum specialist) is advised at least once a year.

2) Tonsil inflammation- redness or inflammation in the tonsils can often also lead to bad breath too

3) Stomach- sometimes stomach pathologies can lead to bad breath. H.pylori (a kind of bacteria) can be present in the stomach, and lead to bad breath. A gastro-enterologist might also need to be consulted. 

Appropriate home care regimens can eliminate most instances of bad breath, and professional help should be taken at regular intervals.