A common reason for bad breath (also called halitosis) is poor oral hygiene, and is often caused by bacteria accumulating below the gumline and on the back of the tongue. This happens when you dont brush and floss your teeth as often as you should, letting food particles linger in your mouth that break down into odor-causing bacteria. There are some cases where halitosis turns out to be a symptom of a non-dental condition, such as diabetes or liver disease, but the majority of those experiencing bad breath are able to correct it with preventative dental care and proper oral hygiene.