A centre of expertise on bad breath (halitosis) is Dr Philip Stemmer's Fresh Breath Centre, at his dental practice in London. He specialises in helping people with intractable mouth odour. "I've a folder full of cases," he says. "One person didn't go out socially for 10 years. It's a serious problem, and we take it seriously."
* About one person in two suffers bad breath to some extent, and most have had it at some time.
* Food is not the main problem - garlic smells of garlic, onions smell of onion, and these smells are temporary. Halitosis is different.
* The smell usually originates in the mouth. It is caused by an accumulation of bacteria - because of trapped food particles, infection or poor saliva flow.
* Brushing teeth helps, especially with flossing, by removing food particles and plaque, but bad cases need a good mouth wash.
* Some mouth washes just mask the smell for a while. Dr Stemmer recommends Dentyl pH (pound;3.99 from larger chemists).
* Do I have bad breath? It is notoriously difficult to know, and there is a recognisable condition - halitophobia - in which an unaffected person becomes convinced he or she has bad breath, and behaves accordingly. Ask a trusted friend, or the dentist. Self-testing is difficult and unreliable, although you can get an indication from the "lick-wrist" test. Lick your wrist, on the bit where people try out perfume samples. Try to go as far back on the tongue as you can, because this back area is often implicated in halitosis. Leave the lick to dry for half a minute, then sniff it. Rough and ready, but gives a hint of what others areexperiencing.
Down in the mouth * Some body odour is natural, and an important part of sexual attraction. The point at which it becomes offensive is partly personal taste and partly culturally determined. We are probably less tolerant now than in the past.
* Fresh sweat is almost odourless. The smell begins when bacteria start working on it.
* Even if your body is sweat-free, your clothing can trap sweat, with bacteria still active.