For a long time, no one really understood the cause of halitosis (bad breath) but, fortunately, researchers have been studying the problem, and we now know what the source of bad breath is. In the vast majority of cases, that foul odor we detect on someone else's breath (and fear on our own) is caused by a group of bacteria living in the mouth. These bacteria are anaerobic, that is, they live in the absence of oxygen, and they produce volatile sulfur compounds (VSC), which smell like rotten eggs.
Everyone probably has some of these VSC producing anaerobes in their mouth: these organism are normal in small numbers, and they simply share the oral territory with numerous other microscopic organisms. In order to become the cause of halitosis, the smelly anaerobes have to multiply to abnormally large numbers, pushing out some of the other organisms. Though it is not yet clear why this happens, understanding what is going on helps researchers to design a bad breath product that will effectively deal with the problem.
The aim of an effective bad breath product should not be to wipe out all bacterial organisms in the mouth, but rather to selectively target the anaerobes that are the cause of halitosis. If the other bacteria can be given the chance to reestablish themselves in normal numbers, the anaerobes can be discouraged from over-multiplying again - don't expect to wipe them all out: even the best bad breath product will only reduce them to small numbers that don't produce a detectable odor. Unfortunately, some people will need to continue treating bad breath indefinitely unless science finds an explanation for why anaerobes multiply in the first place.
Sometimes the underlying condition supporting the bacteria that are the cause of halitosis is obvious. Poor oral health - tooth decay, gum disease, or any other chronic inflammation in the mouth, can create ideal conditions for the odor producers. Chronic sinusitis and post nasal drip can also be a factor. More serious things, like malignancies and lung problems, should also be considered. The best bad breath product will not cure halitosis under these conditions, though it may provide temporary relief.
Nonetheless, though chronic and serious health problems can be the cause of halitosis, the simple answer is usually the right one. If you have reason to suspect a health issue, see your doctor. Otherwise, tackle the VSCs and the unpleasant bacteria producing them by purchasing a quality bad breath product and using it as directed.
R. Drysdale is a freelance writer with more than 25 years experience as a health care professional. She is a contributing editor to Cause of Halitosis , a blog dedicated to the treatment of bad breath.