We normally associate bad breath with the mouth, but just occasionally it can emanate from the nose as nose and mouth are very near to each other, and also have a connection between them at the back of the oral cavity. Sometimes it can be difficult to differentiate one from the other. Sometimes a bad smell can come out of both nose and mouth, as in the case of a regular smoker.

In a regular smoker, smoke pervades the whole of the upper respiratory tract and lungs, causing changes in the resident bacterial population because of the heat from the smoke and its drying effect, and also from thick sticky tars from tobacco, that tend to accumulate on the back of the tongue and in the nose. It is extremely difficult for a smoker to avoid having bad breath to some degree, despite any amount of teeth cleaning or mouth washing.

There are circumstances in which the primary cause of a bad smell is from the nose.This could occur as a result of a blockage somewhere. It has been known for a swimmer to collect debris in the nose causing partial blockage and a consequent low -grade infection. A child can sometimes push things up its nose as part of its normal exploratory behaviour. If it pushes food up there it will slowly rot and cause a bad smell. Rarely a tumour in the nose or sinus can cause blockage of the nasal passages. Even a severe cold can linger on, causing such an excess of mucus that a partial blockage occurs and a secondary infection can be set up. Allergies also can produce excessive nasal secretions amongst other symptoms.

Problems in the sinus, the cavity in the upper face, one on each side, can cause mucus or catarrh to meander down and affect the nose. A chronic low-grade infection of the sinus can cause a post-nasal drip where mucus not only collects in the nose but drips down into the back of the mouth and throat, contributing to the problem.

A problem due to partial blockage or congestion of nasal passages can be helped by the decongesting effect of a suitable vapour, such as that from Olbas oil, Friar’s Balsam, or vinegar. By boiling a quantity of water and adding the agent, you can produce vapours that will help to clear mucus from nasal passages.

Some medical conditions can be associated with a bad smell from the nose, and in these cases the odour tends to be different from the typical hydrogen sulphide smell of halitosis. Some types of cancer, chronic lung infection, kidney or liver disease might cause such a problem. There is also a typical acetone or “pear drops” smell associated with the onset of diabetes, or poorly controlled diabetes. This is due to ketoacidosis, an excess of acetone in the breath that the body is trying to get rid of.

It can be difficult to self-diagnose the problem of bad breath from the nose, as your senses may not register a background smell that is there most of the time. The only real way is to get someone you know to help you out by smelling your breath from the nose. Alternatively you could try the spoon test, by holding the back of a clean spoon under your nose for a minute, then let it air-dry, then sniff to detect any unpleasantness. There may not be enough condensed breath from the nose to detect much though.

If you have a problem of bad breath seemingly exiting through the nose then it is best to see your doctor to determine what the cause might be.