Les tests d'allergie privés en valent-ils la peine ?

What to do if you think you have an allergy?

If you think you have an allergy, the advice from Allergy UK is to start by keeping a food item and symptoms diary to try to identify the offending substance.

GP Dr Mary Harding agrees. She advises her patients to begin with a food diary and then a trial of exclusion, as long as it is a non-life threatening allergy or an intolerance.

"I would also organise some allergy testing if indicated, such as a coeliac screen in someone presenting with abdominal symptoms. If this doesn't help or you have had a potentially life-threatening allergy you may be referred to an allergy specialist."

But there are few NHS allergy consultants, so you may be referred to a different specialist depending on how you present - for example, to ENT, dermatology, or gastroenterology depending on the symptoms. If children are referred, it will often be to paediatricians who will then undertake further tests.

What does the NHS offer?

The NHS can offer the following for food allergy testing and other allergen testing to try to get to the bottom of a potential allergy or intolerance:

Skin prick

Tests cutanés par piqûre - where suspected allergens are scratched on to the arm and a resulting bump or skin redness confirms an allergic response.

Analyses de sang

Blood tests called radioallergosorbent testing (RAST) can also be undertaken. This measures levels of IgE immunity proteins in response to specific substances you could be allergic to.

Patch tests

Other tests may include patch tests where a disc of offending substance, usually a metal, is taped to the skin to see if it triggers an allergic response.

There is robust scientific basis evidence to back up the use of blood testing, skin prick testing et un test épicutané for certain allergens.

Alternative tests

Outside the NHS, a number of companies offer other types of allergy testing. Bear in mind that most of these have little to no scientific evidence of their effectiveness though.

Kinesiology

In kinesiology, muscle responses to certain allergens are tested. The theory behind this is that allergens lead to imbalances in energy levels. There is no evidence to support its use.

Test capillaire

Hair testing looks at the energy fields around hair. It is used to detect recreational drugs but its role in allergies and intolerances is not proven. Indeed, the National Institute for Health and Care Excellence (NICE) actively advises that hair testing should not be used in the diagnosis of food allergy.

Electrodermal tests

Electrodermal testing is based on the concept that there are various energy lines across the body as in acupuncture. The theory is that the skin's electrical conductance at certain acupuncture points is measured and they can be described as 'normal', 'weak' or 'strong' energy levels. You are then given advice as to how to get the correct balance back which may include exclusions of certain substances. Advocates claim that it can also detect vitamin deficiencies. But there is no evidence to support this method for determining allergies or illnesses.

Pulse test

Here, the pulse rate is measured after eating certain substances. According to advocates, an increase in pulse rate >4 beats per minute (>3 if you have type O blood) suggests an allergy or intolerance to the substance. A re-test is performed one month after avoiding the suspected culprit and if a similar reaction is still seen then they recommend avoiding the offending substance again for another month. If after doing this three times you still have a pulse rise, they state that you should avoid that substance altogether. However, this test is not robust enough to detect allergies or intolerances.

Non-IgE blood tests

You even have to be careful about blood tests for allergies undertaken outside of the NHS. There are different types of allergies and different molecules may be involved. NHS blood tests look at changes in immunoglobulin E levels. This protein is involved in what is termed 'immediate' allergic reactions. These reactions produce sudden symptoms, such as tongue swelling, throat swelling and hives.

Some companies offer blood tests measuring proteins other than IgE. These tests are not scientifically proven. They are also costly and easily affected by what you have eaten a few days previously and also by cosmetics, making them less reliable. These tests are leading to unnecessary avoidance of food stuffs and subsequent nutritional deficiencies.

Allergy or fad?

And perhaps you've heard of (or even think you might have) 'leaky gut' syndrome'? This 'condition' has become trendy lately but a good doctor will tell you it's nothing more than a fad.

In 'leaky gut' it is hypothesised that food allergens pass through a damaged gut wall and enter the bloodstream, leading to illnesses such as le syndrome de fatigue chronique. And yet, there is no evidence to support this. The gut wall is actually pretty impermeable - there are a few medical conditions when it can become leaky, such as maladie de Crohn, but as a cause of other illnesses there is no proof.

Gut bacterial overgrowth on the other hand, does exist but is not thought to be the result of food allergy or symptoms of food intolerance. It usually follows a seriously bad stomach infection or occurs in those with la maladie inflammatoire de l'intestin. It can be also be a factor in some cases of le syndrome du côlon irritable. In the majority of cases it will resolve spontaneously and without medical input. If you think you might have bacterial overgrowth do not just treat it blindly, see your GP and ask about referral to a gastrointestinal specialist who can, if appropriate, test for it and provide the correct treatment.

In conclusion

Which allergy tests are worth paying for? The short answer is: none of them. If you suspect you have an allergy or intolerance, go to your GP. If you are referred to a specialist they will go through your symptoms and try to work out which allergens might be the culprit and which tests will be best. Be warned though, you may have to wait some months before your first appointment. Use this time to keep a symptom diary. It's also worth checking the BSACI website to find NHS allergy specialists.