Halitosis (bad smelling breath) usually comes from the mouth because that’s where it’s produced: bad breath out of nose passages may be sign that something more complicated is going on. Most sources agree that the hydrogen sulfide smell so typical of halitosis is caused by the production of volatile sulfur compounds by bacteria living in the moth. When air is expelled from the mouth, the odor is detected. When air is expelled from the nose, the air comes from the lungs and bypasses the mouth, so it’s unusual for air coming from the nostrils to smell bad.
Bad breath coming thru the nose is more likely to originate in the nose, sinuses, or throat, or even more unusually, from the lungs, lower airways or stomach. The first step is to confirm the existence of bad breath out of nose passages – your sense of smell might be off due to a viral infection or anything else that causes sinus irritation. Are you suffering from dry nose, allergies, a cold, or anything else that might be affecting your sense of smell? Your bad nose breath may be an illusion – have a good friend confirm that it’s real before you overreact.
Bad breath out of nose passages may be caused by a blockage or obstruction in the nasal passages that is preventing normal airflow and drainage. Individuals, especially small children, sometimes push objects into their nostrils that may then become lodged in the airway. Swimmers may inadvertently inhale objects in water if they take in water through the nose. Occasionally undigested food gets lodged in the sinuses when an individual vomits. Any of these things can set up a situation that will result in bad breath coming through the nose.
Bad nose breath can also be a result of infection in the nose or sinuses, or even in the throat or lungs. Infection, however, seldom happens without other symptoms. If the person experiencing bad breath out of nose passages has swelling, redness, heat, or pain in the sinuses, an infection may be brewing, and a doctor should be consulted. Similarly, lung and throat infection typically also cause pain and fever. Bad breath coming thru the nose is an incidental sign of these infections that is distant from the infection itself.
Some medical conditions can result in bad breath out of nose passages; however, the odor noted in these cases is usually different from the typical hydrogen sulfide smell of halitosis. Some malignancies (cancer) of the airways can cause an odor, as can kidney and liver disease, and ketoacidosis (a serious complication of diabetes). Again, though bad breath coming thru the nose is noted, the odor comes from elsewhere. See your doctor if you notice bad nose breath and there is no obvious reason for it, especially if you are feeling at all unwell.