B ad breath (halitosis) can be an embarrassing problem for children as well as adults. Halitosis is an unpleasant odour which comes from the mouth or nose and occurs when exhaled air contains more than 75 parts per billion of odorous sulfurous compounds. These are produced by the build-up of bacteria that decompose sulfur-containing compounds to release hydrogen sulphide that smells of rotten eggs. Halitosis may be a sign of diverse conditions and the mouth is the cause in 85 per cent of affected individuals.
Post-nasal drip is probably the commonest cause of halitosis in children as secretions from a sinus infection, runny nose or nasal allergy drip down the back of the throat onto the tongue. Odour-causing bacteria thrive on these secretions which are rich in sulfur-containing compounds.
Conversely, other oral causes of halitosis include a dry mouth which may be enlarged adenoids leading to chronic mouth breathing and therefore a dry mouth, a decrease in the flow of saliva which is very important because it cleanses the teeth and mouth, and destroys oral micro-organisms (e.g. reduction in saliva due to salivary gland disease). A dry mouth may also be caused by medications such as antihistamines, antipsychotics, bronchodilators, antidepressants and antispasmodics.
Other causes of halitosis include stagnation of saliva in the mouth, build-up of gram-negative bacteria due to a less acidic mouth pH than normal, an increase in the amount of protein in the diet, and an increase in the number of dead oral lining cells in the mouth. Many of these things may be caused by alterations to the bacteria in the mouth, and this may be caused by intercurrent antibiotic therapy (which may also allow fungal infection of the mouth, a cause itself of foul breath), chemotherapy or diabetes. Oral disease that may cause halitosis also includes abscessed teeth or dental caries, both rich sources of bacteria. Faulty dental restorations or poorly fitting crowns may also allow food and bacteria to accumulate and putrefy, producing a foul odour. Oral cancer and its treatment causes tissue destruction and bleeding, and this cellular debris is a fertile breeding ground for bacteria. Sinusitis or a foreign body lodged in the nose or respiratory tract will provoke an inflammatory response with a foul-smelling discharge.
Tonsillar disease or deep crypts in the tonsils may accumulate food and may also produce a foul odour.
Prevention of halitosis depends on eliminating the cause, and an obvious and useful first step is to ensure adequate oral and dental hygiene.

Source: Weekender, March 21,, 2009