Do allergy tests really work?

Like thousands of Londoners, I worry whether that mysterious rash or sudden upset tummy is down to a hidden allergy I have been completely unaware of. Certainly, people seem more willing to ascribe themselves intolerances or allergies, sometimes by just looking at a food label.

Personally, on some days, for no clear reason, I develop a set of mysterious symptoms that leave me feeling flat, sometimes exhausted. Occasionally it's nausea or a feverish sweat; at other times my energy levels suddenly and inexplicably slump. I get hay fever, too - and while I know it is caused by certain pollens, nutritionists have suggested it could be exacerbated by eating the wrong foods. But I wanted to find out once and for all, so I tried the most popular allergy tests to see what my tolerances really are.

Cambridge Nutritional Sciences

93 Food IgG Test. COST: £199

What is it? An at-home pinprick blood test which looks for antibodies produced for 93 common foods.

This test, available over the internet or through nutritionists, is called an enzyme immuoassay. It identifies food allergies by looking for IgG antibodies in a blood sample. Unlike IgE antibodies, which cause immediate allergic reactions such as hay fever or asthma, IgG antibodies produce allergic responses 24-48 hours after exposure to the irritating substance.

What foods should I avoid?

Strong allergic reaction to egg white, which I was advised to cut out from my diet for at least six months. I have less severe reactions to egg yolk, cow's milk and cola nut. I should reduce my intake of these foods, including milk-based products such as yoghurt, cheese and cream. I was quite surprised to find I have an allergy to cola nut, as this is something I hardly ever eat.

Experts say: Muriel Simmons, of Allergy UK, says: "We funded research by York University which looked at 5,000 people who did IgG tests - 70 per cent were still experiencing benefits after a year of excluding their 'allergic' foods. We're impressed with this test.î

Patrick Holford, nutritionist and founder of the Institute for Optimum-Nutrition, says: "This is one of the most reliable tests for food intolerance. It directly measures molecules that the body makes to fight invaders - but in this case, the body mistakes foods as a harmful invader.

"The results from this type of test can usually be accurately reproduced," he adds. "The only disadvantage is that it won't detect allergic foods that you haven't eaten for three or more months."

Rating: *****

Aeon Biotech Ltd

NuTron Test. COST: £245

What is it? Available over the internet, NuTron sends you to a nearby clinic, where a blood sample is taken and sent to its laboratories for analysis. There, the blood sample is put in contact with 90 food samples and incubated. The blood is then analysed for white blood cells called neutrophils - in allergic reactions, these are produced to attack foods as if they were foreign invaders.

What foods should I avoid? This was the list, starting with the foods I was told I was most allergic to: pork, malt, beetroot, haddock, egg yolk, egg white, sunflower seed, coffee, lamb, courgette, prawn, halibut, carrot, celery, turkey, wheat and herring.

I haven't eaten meat for three years (I do eat fish), so it seems strange that pork was listed at the top of my food-allergy list. As there are so many foods to avoid I'd find it very hard to stick to the suggested diet plan.

Experts say: "There isn't enough independent research on this test for us to say whether it's good or bad,î says Muriel Simmons. " People are sometimes given long lists of food to avoid but the company offers dietary advice to ensure they get the nutrients they need.î

Patrick Holford says: "When neutrophils come into contact with a food allergen, they start enlarging and can explode, releasing substances that attack the allergen. This test looks for enlarged neutrophils, but there is a danger of it producing false positive results."

Rating: ***

Kinesiology muscle testing

COST: £45 for one hour at Naturework, London,W1. Then £60 to see a second kinesiologist at the private Alternative Health Centre in Hampstead

What is it? According to this muscle-testing technique, substances to which the body is allergic cause muscular weakness. The practitioner places a food sample against the client's skin, and tests their muscular tone by exerting gentle pressure against their upper or lower arm. I went to the second kinesiologist to compare the results.

What foods should I avoid? The first kinesiology test found I was allergic to brown rice, courgette, ginger, tofu, ham, cheese, carob, chicken, carrot, onions, wild blackberries, strawberry, raspberry, grapefruit and rhubarb. The second test found I was allergic to chicken, cheese, eggs, yeast, bananas, lentils, prawn, leek and onions. The completely different results make the technique seem rather random.

Experts say: "There is limited evidence to show that this test has any validity - I'd urge extreme caution before paying money for this sort of test,î says Muriel Simmons.

Patrick Holford adds: "Certain substances - including foods - do induce muscular weakness and this is a well-recognised phenomenon. However, muscular weakness doesn't necessarily mean you have an allergy, and there is a lot of room for subjectivity."

Rating: **

The Biocom test

COST: £140 for two hours at the Hale Clinic in W1

What is it? This method reads electrical frequencies along energy lines, which correspond to the meridians of ancient Chinese medicine. Allergic reactions are identified when the electrical frequencies are higher or lower than limits recognised as healthy.

The Biocom machine is used to detect hay fever and asthma, as well as food intolerance. Placing their bare feet on a metal plate, clients hold an electrode in their hand - food samples are then placed in the electrical circuit and a reading is taken.

A reading of 50-60MHz is considered healthy. Higher frequencies indicate that the substance is stressing the body, while lower frequencies indicate there has been a "collapse" as a result of excess stress.

What foods should I avoid? Yeast, wheat, buckwheat, gluten, milk, mushrooms and cherries. I was advised to cut these out for at least three months, before reintroducing them slowly, in moderate levels.

I could see the readings on the machine for myself, but couldn't be sure if the readings given by dried food samples could really compare with their fresh counterparts.

The results appeared random compared with the other test results and I hardly ever eat buckwheat or cherries.

Experts say: "This method hasn't been scientifically validated. Our worry is that people may be given long lists of food to avoid with little dietary advice," says Muriel Simmons.

In the end, I took the advice of the IgG test. The science behind it is widely recognised and the list of allergy producing foods was the shortest, making an exclusion diet easy to follow.

For the past month, I've been avoiding eggs - with the occasional lapse - and have cut my intake of dairy products to a minimum. In the first two weeks, I suffered one bout of mild fever and a slight energy slump. I've had the odd allergic-sneeze, but nothing close to a hay-fever attack.

Last week, when I ate an egg and I felt a little off-colour two days later, I became convinced that there is a connection between diet and the mysterious symptoms I used to suffer.