More than a third of us believe we have a food allergy. Yet doctors put the figure at a mere two per cent. So are we just imagining our symptoms? Julia Stuart reports

Two years ago, Michelle Gibbs noticed that the area underneath her eyes had started to swell. It was so disfiguring that the 37-year-old mother-of-two from Gidea Park, Essex went to her GP. Eventually, Michelle was referred to an allergy specialist at the London Chest Hospital, and told she had a food intolerance. It is still so severe that at times she worries people think she has been beaten up.

Two years ago, Michelle Gibbs noticed that the area underneath her eyes had started to swell. It was so disfiguring that the 37-year-old mother-of-two from Gidea Park, Essex went to her GP. Eventually, Michelle was referred to an allergy specialist at the London Chest Hospital, and told she had a food intolerance. It is still so severe that at times she worries people think she has been beaten up.

According to the charity Allergy UK, 45 per cent of the population suffers from symptoms that are related to the food they eat, a dramatic increase over the last five years. Yet doctors say that food allergy affects a mere 2 per cent of us - so what is wrong with the other 43 per cent? Some would call them "food intolerant", but there is confusion as to what the definition of food intolerance is - or even if the condition exists at all.

Food allergy is an adverse reaction by the immune system, which can be detected by a blood test and may be life threatening. Food intolerance, however, does not involve an immune reaction, but it still makes the sufferer feel unwell and can have a major impact on their working and social life. Sufferers usually complain of fatigue, headaches and indigestion. In some cases, there have been reports of vomiting, diarrhoea and wind. Diagnosis is usually by a blood test or an elimination diet.

A survey by the Food Standards agency in 2002 found that more than 30 per cent of people believed themselves to have a food allergy, a considerably higher figure than the real one. They put the discrepancy down to a rise in "inaccurate self-diagnosis" and a confusion between what constituted a food allergy and a food intolerance. Others have also blamed a growing psychological sensitivity to foods.

Tom Sanders, professor of human nutrition at King's College London, says: "Psychological food intolerance involves people who believe that when they eat a food it has an adverse effect. But when you challenge them with the same food fed through a tube [so they are unaware of what they are eating], it has no effect."

The charity Allergy UK is devoting this week to publicising food intolerance. Its chief executive, Muriel Simmons, says that incidences are increasing because we are eating things that weren't available to us just a few decades ago, such as kiwi fruit and avocado. "Because we are now far more adventurous with our food, we are likely to find things that we like but our bodies don't always like," she says. "And we don't rotate our foods any more. If we like things, we tend to eat them all year round because we can get them all year round."

Patrick Holford, a nutritionist and author of New Optimum Nutrition Bible, estimates that one in four of us has a food intolerance or allergy. The most common culprits are dairy, yeast and wheat. "We know that hunter-gatherers did not consume wheat, and for the large part did not consume milk. It's relatively new to our organism, that's the first probable reason. There is also more gluten in grain. The bread we eat today is very different from the bread we ate pre-Industrial Revolution, and we eat tons of it, about six servings a day. One of the things that increases your risk of being intolerant to cow's milk is if you consume it before the age of about four months. It takes a few months for an infant's gut to form properly and it takes a while for their immune system to develop. As for yeast, one imagines hunter-gatherers weren't having fermented food. The other reason for the increase in food intolerance is possibly that our immune systems are less strong. The 21st century is stressful and we are exposed to more pollutants."

Another reason, of course, is that believing you have a food intolerance offers an easy solution to your problems. It is easier to blame wheat for your fatigue, weight gain and lethargy than to take responsibility for the fatty, sugary foods you eat, and the fact that you don't exercise or get enough sleep, you hate your job and you're in an unhappy relationship.

A study in the journal Social Cognition in December found that many food intolerances could be imaginary. Psychologists at the University of California, Irvine, found that when people were told - falsely - that a particular food had previously made them ill, many people later reported an intolerance to that specific food.

Nigel Denby, a registered dietitian, agrees that there has been an increase in food intolerance and allergies, but says that it is not as high or significant as people think. "I believe the number of people who have a food allergy or intolerance is fewer than 5 per cent. I think it has become such a topical issue because we live in a fast-moving, quick fix society. Many of the dietary issues that people are facing, whether it be irritable bowel syndrome, being overweight or simple indigestion, are a result of the pace of the life that we live and the types of food we choose - heavily processed convenience foods - as well as the way we eat on the run.

"Very often, it's easier to make the culprit something that appears to be as simple [to solve] as a food intolerance, rather than addressing several areas of your life. It has also been fuelled by celebrities saying that [discovering] a food intolerance or allergy has been the saviour of all their problems. It's a very attractive option: 'Let's just cut a certain food out and that's the end of it.'"

Denby is particularly concerned about the number of people who set themselves up as nutritionists with varying qualifications, offering tests that have little or no scientific basis. "I think that when you have a vulnerable public looking for easy solutions there always has to be the risk of people making an awful lot of money out of it."

He dislikes Vega testing, which measures the resistance to a food by using electrical currents, and Kinesiology, where droplets of food are placed on the tongue with the arm extended forward. The way the arm swings in response to the food supposedly gives the therapist an indication of whether there is an intolerance or not.

"They really have very little merit," says Denby. "Skin-prick tests can be useful, but it's a very skilled operation and should only be carried out in a specialist allergy clinic. We see an awful lot of people who have been misdiagnosed and, even more worrying, been given very insubstantial information on which to base any dietary change. It's no good saying to someone, 'just cut out wheat', because to a lay person that means bread and Weetabix. In actual fact, wheat is used in many foods as a stabiliser and thickener. It's often hidden, so if someone does have a real problem with wheat, they need quite concentrated coaching from a registered dietitian."

He says the only accurate test for a food intolerance is to use a variety of exclusion diets, which means either removing a food completely from the diet and monitoring symptoms, or eating relatively few foods and reintroducing one food at a time. "It's very time-consuming and needs an awful lot of support from a dietitian."

Since Michelle has been following her NHS dietitian's advice, and cut out food containing moderate or high amounts of salicylates, which are present in some fruits, vegetables, alcohol, tea, seasoning, nuts and seeds, she has seen some improvement. "The symptoms went in the summer then came back when I ate a damson pie," says Michelle. "Then, we went to a friend's last weekend and ate Chinese. I thought I'd have something plain - plain rice and lemon chicken with a white wine spritzer - but my eyes came up. It feels as though something has bitten me under the eye, where the bags are, and it starts to swell and goes red and then fills with a fluid. When the fluid subsides it then goes baggy. Then you are left with lines like a deflated blister.

"It's very hard to go out and not eat certain foods. People think I'm a silly woman with a stupid eating fad. I've been really down about it in the past - I've just been out with friends, for example, and I had to take my own lunch. It can make you very depressed."

Allergy UK's Simmons recommends that people who believe they have a food intolerance should keep a food diary of everything they eat and drink. "It's quite difficult with food intolerance because it's rarely an immediate reaction. It can show up anything up to 48 hours later. But you can often identify a pattern, and it's worth cutting that food out for a time and seeing whether that improves things."

The effects can be dramatic. The charity had to plan a route to work for one woman with such bad irritable bowel syndrome that she needed to use the toilet several times during the journey, but once her intolerance to yeast was identified, she recovered.

Simmons recommends, however, that those who feel generally unwell should always see their doctors, as their symptoms could be caused by something else.

Allergy UK (01322 619864;