Bad breath is a common problem that can cause much personal distress. The technical term for the condition, halitosis, comes from the Latin halitus (breath) and the Greek osis (abnormal). Halitosis is now undergoing close scientific scrutiny, which it is hoped will soon yield effective treatments to deal with this embarrassing problem. This work is described by Mel Rosenberg in the April 2002 edition of Scientific American.
A recent survey indicates that about one in three families have at least one member with habitual bad breath. I know from having lived there that North American society is particularly conscious of halitosis. US supermarkets are stocked with a wide variety of mouthwashes, dental rinses, breath mints, dental chewing gum and so on. In the year 2000, the American public spent over $1 billion on oral care gum, mouthwashes and other breath fresheners.
Eighty-five to 90 per cent of halitosis cases originate in the mouth and are primarily caused by gaseous emissions by oral bacteria. The mouth is inhabited by hundreds of bacterial species that feed on the food we eat. They are particularly fond of protein, and some of the chemical products that result from their digestion of protein account for the bad smell.
Some of the principal malodorous compounds emitted by these bacteria include: hydrogen sulphide (rotten eggs smell); methyl mercaptan and skatole (faecal smell); cadaverine (rotting corpse smell); putrescine (rotten meat smell), and isovaleric acid (sweaty feet smell).
Recent research has discovered previously undescribed species of bacteria that live in our mouths and has also shown that bacteria that live on the tongue differ from those that live in plaque on teeth.
The main source of bad breath in people without the complications described later is the back of the tongue and not the teeth and gums. This area contains many tiny cracks in which bacteria and oral debris accumulate. Post nasal drip also collects in this region in about one quarter of people studied, and the bacteria putrefy the rich mixture of nasal drip and debris.
It is quite possible to suffer from bad breath even if you practice good oral hygiene; but if you don't, that in itself can cause bad breath, particularly if protein particles are left between the teeth. Other oral sources of bad breath include inflamed gums, faulty dental work, dirty dentures and abscesses.
A steady flow of saliva washes bacteria and their smelly emissions away and, conversely, factors that promote dry mouths, such as mouth breathing, fasting, stress and many medicines, can worsen the problem. Cigarette smoking dries out the mouth and worsens gum conditions and post-nasal drip.
It might be thought that the best treatment for halitosis would be to eliminate all oral bacteria. However this cure would be worse than the disease. Our tongues are also home to small numbers of a yeast-like fungus that is kept in check by the bacteria. If the bacteria were eliminated, the fungus would proliferate into a condition more difficult to control than halitosis.
After the mouth, the most common source of halitosis is the nose and nasal passages, accounting for five to 10 percent of cases. Nasal odour may be caused by sinusitis or conditions that impede mucus flow. Putrid tonsils may cause about three percent of cases. Contrary to popular belief, the stomach is rarely a source of bad breath.
Many people have bad breath but are not aware, or not fully aware, of the problem. We are all sensitive to the slightest whiff off someone else's breath but are notoriously bad at smelling our own.
So, what can you do if you suffer from halitosis? Rosenberg advises as follows:
•Gently sweep the mucus off the back of the tongue with a plastic tongue cleaner
•Eat a good breakfast - it cleans the mouth and enhances saliva
•Drink plenty of liquid/chew gum to prevent mouth dryness
•Rinse and gargle with mouthwash just before sleep
•Brush and floss your teeth properly
•Clean your mouth after odorous foods
•Ask a close friend, or family member, to check your breath.
Some people suffer from an exaggerated fear of having halitosis - halitophobia. One survey found that 16 per cent of people worried "a lot" about how their breath smelled and three percent said breath worries interfered with their lives from a moderate to severe amount.
Many of these people do not have bad breath. They may misinterpret bad taste as a sign of bad breath or the behaviour of others, such as opening a window. Halitophobics who acknowledge the possibility of a psychological basis for their fears can often be helped by psychotherapy.
And finally, a little joke: Mahatma Ghandi walked barefoot, which produced an impressive set of calluses on his feet. He also ate very little which made him frail and gave him bad breath. All of this made him . . . what? Answer: A super callused fragile mystic hexed by halitosis.
•William Reville is Associate Professor of Biochemistry and Director of Microscopy at UCC
•Our columnist Dr Reville has been appointed a member of the Irish Council for Science, Technology and Innovation, established in 1997 by the Government to advise it on the strategic direction of science, technology and innovation policy. The Council is chaired by Dr Edward Walsh, University of Limerick.