The Knack: Avoid onions, pizzas and peppermints, says dentist Philip Stemmer
"Bad breath is caused by an excess of bacteria in the mouth which gives off smelly gases called volatile sulphur compounds. Avoid bad breath by good oral hygiene - brushing, flossing, toothpicks. And don't eat hot dogs, onions, garlic and pizza - you'll smell of them. A dry mouth makes breath worse, so avoid things that dry the mouth such as smoking, drugs and alcohol, especially wine, and don't fast or over-exercise. Don't suck peppermints: it causes decay and only covers the problem, as do most mouthwashes, which last 15 minutes. The best way to find out whether you have bad breath is to ask a partner or confidante, or do the Rosenberg Wrist Test.

Stick your tongue out as far as you can and lick the inner surface of the wrist, where ladies put perfume. Wait four seconds and smell.

How one gets rid of bacteria depends on the cause. We make a diagnosis and treat the problem using chemical preparations and mechanical devices.

We have tools, sticks and brushes for every eventuality - like the tongue cleaner. If patients do what we say, it takes between two and four weeks for them to have breath so pristine it can't be noticed.

Most patients have had the problem for 10 to 20 years, and hundreds contemplate suicide. We treat lords, street sweepers and pop stars. Our age range is nine months to 84 years old. We also see a lot of halitophobics, people who think they've got bad breath and haven't"

Philip Stemmer is a leading dental surgeon at the Fresh Breath Centre in west London (0171-935 1666)