Bad breath generally comes from improper oral hygiene. The most common culprit is fairly easy to understand: Food particles that remain in your mouth for long periods of time are broken down by bacteria. That process produces sulfur compounds in your mouth that—you guessed it—smell unpleasant. Other causes for bad breath can include smoking and tooth decay.
To control bad breath, the simplest advice is to brush and floss regularly. Additionally, staying hydrated, and thereby preventing a dry mouth, will also help to reduce mouth odor.
Yes, more serious health problems can be linked to bad breath, but in the majority of cases, bad breath is due to the reasons described above. If you have questions or concerns about bad breath, be sure to bring them up with your dentist.