Bad breath commonly results from bacteria feeding on food stuck in your teeth and gums. The simplest treatment, in that case, is good oral hygiene: proper brushing and flossing.

Other common causes include post-nasal drip (leaking sinuses), infected gums, bad heartburn (acid reflux) or not eating or drinking anything for a while. On rare occasions, more serious causes can be identified, such as oral abscesses or even oral cancer.

Chances are, it isn't serious. Your doctor can easily help you sort out the cause and ways to treat it.