Though bad breath is typically thought of as being emitted by the tongue, teeth, gums, palate and throat, plenty of research suggests that it can also come from a fairly unexpected place - the nose.
Oral odor is caused by the presence of bacteria in the mouth. As these microbes consume sugars, proteins and food particles, they emit aromatic compounds that give exhaled air its pungent smell. However, not all protein consumed by these microorganisms come from food.
Nasal mucus caused by sinusitis give oral bacteria plenty to consume, particularly when postnasal drip forces this fluid down the back of the throat. Coughing or sneezing can add to the problem, as particles are forced up through the tonsils and across the tongue.
Occasionally, halitosis can be a symptom of severe nasal conditions. A recent issue of the American Journal of Respiratory and Critical Care Medicine noted the case of a 66-year-old woman whose chronic cough and bad breath ultimately revealed the presence of necrotizing rhinosinusitis, in which the nasal tissue had been inflamed for so long that it had begun to decay.
While this condition is relatively rare, postnasal drip isn't. Treating oral odor caused by nasal problems often means looking into specialty breath freshening products.