Preliminary trials involving patients avoiding some of these foods have had encouraging results, they add.

The research, by St George's Hospital in London, is published in the American Journal of Gastroenterology.

It opens up a new avenue for the management for this large and complex group of patients

Professor Devinder Kumar

It is estimated that IBS affects a third of the population, and about one in 10 people suffer symptoms bad enough to go to the doctor.

Symptoms vary but may include abdominal pain and spasm, diarrhoea, constipation and bloated stomach.

Scientists found patients with different types of symptoms, such as diarrhoea and constipation, showed signs of food hypersensitivity.

Body response

Researcher Professor Devinder Kumar said: "Symptoms from the irritable bowel syndrome can compromise the quality life.

"With this simple test, we have scientifically shown that these symptoms may be due to the body's response to what we eat in our daily diet.

"It opens up a new avenue for the management for this large and complex group of patients."

Current research suggests that around 5% of the general population has a hypersensitivity to food.

However, up to 65% of IBS patients believe their condition may be linked to food allergy.

There are food intolerance tests which have helped to identify IBS in some people.

But Dr Mark Cottrill, a GP and member of the IBS Network, told the BBC News website: "Everybody wants one magic pill to cure IBS, but it is probably a multi-factorial condition, which has different causes in different people."

Dr Cottrill said it was possible that in some people IBS was related to a failure of the natural painkilling system to block the discomfort generated by normal movements in the bowels.

Alternatively, the condition has been linked to bowel inflammation brought on by infection.