A study by a food diagnostic company discovered that many hypochondriacs have changed their diet after carrying out self diagnosis on the internet.
And incredibly one in 50 reckon they only noticed the condition when a friend had similar symptoms.
The research, which was carried out by www.yorktest.com to mark food tolerance week, also revealed 39 per cent of people think it's trendy to declare themselves food intolerant.
Almost 12 million claim to be food intolerant - but less than a quarter of those have had it medically diagnosed.
Olympic gold medallist Denise Lewis is a typical case of a sufferer who has guessed what the problem is and denied herself her favourite foods for years.
She said: ''I've suffered from IBS related symptoms for the past 13 years and these have affected my performance on and off the track.
''I was often guessing what could be wrong with me and eliminating a range of foods I thought could be the problem.
''After taking a YorkTest food intolerance test I found out I was intolerant to cow's milk, egg yolk and garlic.
''Since reducing these from my diet I've not suffered my usual bloating and stomach cramps, have more energy and feel brighter and lighter. My stomach has healed itself and I can even tolerate a little bit of those 'forbidden foods' in my diet once again.''
A spokesman for www.yorktest.com said: ''Food intolerances are on the increase but it's worrying to think that many sufferers have never actually been tested or diagnosed.
''There is a surprisingly diverse range of foods which people are now intolerant to.''
Nutrition expert Patrick Holford says that people spend decades suffering unnecessarily from hidden food intolerances because most doctors aren't aware of the symptoms than can be caused, and cured, by avoiding unidentified food intolerances.
Mr Holford said: ''I suffered for twenty years from crippling migraines, ear infections and sinus problems before identifying that the problem was a food intolerance.
''People who feel tired, or have digestive problems, or eczema, asthma or joint aches often have a food allergy or intolerance. Likewise headaches or depression are often symptoms of hidden food intolerance.
''Food intolerance symptoms aren't as severe as food allergies; so many people might not want to worry their doctor about them and will just blame it on the busy, hectic lifestyles we lead.''
Twenty two per cent of the 1500 polled have to put up with constant sneezing and 18 per cent having a stuffy nose.
Another 13 per cent suffer from hives while 11 per cent even have a shortness of breath thanks to their allergy or intolerance.
The range of foods people are intolerant to is incredibly diverse with grapefruit and sushi being named as two of the worst offenders
Patrick Holford added: ''Some suffer for years unnecessarily but food allergies are caused by IgG antibody reactions to food.
''By identifying what you are allergic to, avoiding it for three months and following an anti-intolerance diet, most people can grow out of these IgG based intolerances and go back to eating their favourite foods again.
''By taking a simple and clinically proven test such as YorkTest, consumers can diagnose over 130 potential culprit foods within a couple of weeks, saving months of guess-work and hours trying to get an appointment with their doctor.''
Some believe it's a condition fuelled by celebrities with 38 percent blaming faddy and celebrity diets for an increase.
Sixteen per cent of those polled said there are not enough products on the market to help identify or prevent their food intolerance.
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