Chapter 20.2, Problem 1HYEW

Unpleasant breath odors are caused mainly by prokaryotes that live in the mouth. The warm, moist human mouth cavity hosts a diverse microbial community that includes more than 2,000 prokaryote species. Many of these species acquire energy and nutrients by breaking down mucus, food particles, and dead cells.

The by-products of this breakdown can include foul-smelling gases, some of which are also emitted by feces or decaying bodies.

The highest concentration of bad-breath prokaryotes is found at the base of the tongue. This location may be especially hospitable to microbes owing to the accumulation of mucus that drains down into the back of the throat from the nose. So, if you gargle with antiseptic mouthwash to control bad breath, thrust your tongue forward so the mouthwash can reach the base of your tongue.

What Causes Bad Breath?