Bad breath (halitosis) is socially unacceptable and seeing people wince and turn away from you when you speak does little for your self esteem. Self-diagnosis is, however, difficult as it is not possible to easily detect an odour from you own breath. Those who have halitosis are often unaware of it until they have been informed by friends or relatives. People who have been told that they suffer from bad breath may continually worry that an offensive smell can be detected from their breath.

Halitosis is a common condition caused by sulphur-producing bacteria that live within the surface of the tongue and in the throat. Sometimes, these bacteria start to break down proteins at a very high rate and odorous volatile sulphur compounds (VSC) are released from the back of the tongue and throat. Halitosis is not infectious. About 2.4% of the adult population suffers from bad breath.

Apart from the sulphur-producing bacteria that colonise the back of the tongue, the other major causes of halitosis are:

• dental factors – such as tooth decay, periodontitis (infection around the teeth) or poor oral hygiene. These are the commonest causes of bad breath.
• dry mouth (xerostomia) – caused by medicines, alcohol, stress or a medical condition
• smoking – which starves the mouth of oxygen.

Less common causes of halitosis include:

• acid and bile reflux from the stomach
• post-nasal discharge – for example, due to chronic sinusitis
• kidney failure, various carcinomas, metabolic dysfunctions, and biochemical disorders, together account for only a very small percentage of halitosis suffers
• other medical conditions such as bronchiectasis, bronchitis, diabetes
• medication – some types can cause bad breath, for example nitrates, some chemotherapy drugs and tranquilisers
• crash dieting – fasting, low carbohydrate and high protein diets cause the body to break down fat, which produces chemicals called ketones that can be smelt
• foods - such as onions, garlic or cauliflower, which induce certain odours. However, these effects are only short-lived.