Giles finally went to seek help at the Fresh Breath Centre in London, run by dentist Dr Philip Stemmer. Dr Stemmer put Giles in touch with members of his newly formed support group, Halitophobics Anonymous. "I talked to someone who had it so bad that they didn't leave their house and only spoke to friends on the telephone," says Giles. "They had been suffering for 13 years compared with my one. I'm so glad I sought help because the paranoia was slowly getting worse and I'm sure I would have ended up a recluse."
Halitophobia, the unfounded fear of having bad breath, is, like anorexia and bulimia, a modern disorder, mainly caused by our obsession with appearance, encouraged by advertisers' portrayal of a world full of happy, beautiful people. Dr Stemmer, whose centre's aim is to cure people with genuine halitosis - a condition that affects most adults at some time and about half of adults all of the time - has noticed more and more people presenting themselves to him with halitophobia. "I began to realise this was a serious psychological problem, with some people drastically curtailing their social lives to the point that they would not go in lifts, buses and trains - even go out at all," he says. "The interesting thing was that, even having been told by friends and professionals that they did not have a breath problem, they still would not believe that they did not have smelly breath."
According to Mel Rosenberg of Tel Aviv University's School of Dental Medicine and the world's leading expert on halitosis and halitophobia, the condition is part of a group of psychoses called Body Dysmorphic Disorder. He says, "Sufferers, particularly women, get obsessed with an aspect of their physique - their nose is too big, their ears stick out - and the obsession takes over their whole lives, leading to serial nose jobs or, in the case of halitophobia, increasing isolation."
Rosenberg points out that there has been one recorded case of suicide due to halitophobia and other cases of the condition leading to marital break up and sufferers becoming virtual recluses. "About one per cent of the population suffers from halitophobia, but recognition of the problem is in its infancy, so doctors don't know how to treat it," he says.
Halitophobia and other types of Body Dysmorphic Disorder (BDD) are best treated with gentle counselling and therapy and discussions with fellow sufferers. Dr Stephen Palmer, who runs the Centre for Stress Management in London, has treated many people for BDD - for example, people who are convinced their bodies are covered with unsightly warts. "In the case of warts, people look in a mirror and do not see reality, or they have old chicken-pox scars, which they think are obvious and ugly."
Dr Palmer believes this pursuit of perfection is a western problem, mainly caused by advertisers using teenagers to promote clothes for women and Mr Universe types for shaving products and sportswear. In the case of bad breath, at one end of the scale we use more mouthwashes than before - sales have doubled to pounds 72 million in 10 years - at the other, halitophobics are born.
As for curing halitophobia, Dr Stemmer says, with charming honesty: "You could pay a lot to come and see me, but first ask your partner to tell you whether your breath smells, and if they say no, take their word for it."
Fresh Breath Centre, Conan Doyle House, 2 Devonshire Place, London WIN IFA, 0171 935 1666.