Michelle Berriedale-Johnson attempts to
chart a course through the complexities of allergy testing.

Like so much in the field of allergy, testing is bedevilled by terminology.

Procedures as varied as a RAST blood test for peanut
allergy carried out in a hospital allergy clinic, a postal IgG food intolerance blood prick test or a health food store Vega food-intolerance test are all referred to as ‘allergy tests’ - thus invoking the fury of mainstream allergists who point out, quite correctly, that most of these tests are completely useless for diagnosing classic, Type 1
immediate hypersensitivity.

However, the majority of the non-hospital based tests are not intended to diagnose classical, Type 1 allergy; they are attempting, with more or less validity, to address the problem of illnesses which appear to be triggered, or at least made worse, by the ingestion of certain foods or the contact with (or inhalation of) certain substances ranging from
peppers to pesticides.

Test validation

The mainstream medical profession object to most of these tests on the grounds that that have not undergone sufficiently thorough clinical evaluation and have not been subjected to the gold standard of medical research, the double blind placebo controlled trial. The problem is that the very individual nature of allergy/sensitivity, and therefore testing for it, makes it almost impossible to use conventional evaluation methods which require a level of uniformity amongst those tested to enable comparison.

The immune system
An ‘allergic reaction’ is commonly assumed to involve the immune system, yet many symptoms that may suggest that the patient is having an allergic reaction to a food, chemical, mould, pollen etc may not involve the immune system at all.
In medical speak, however, the term allergy indicates an immune system reaction.

The immune system is designed to protect the body against harmful invading micro-organisms which include proteins, polysaccharides,
bacteria and viruses. It both recognises and remembers these substances, which are known as antigens.

However, it appears that sometimes the immune system gets it wrong and identifies a perfectly harmless substance - a peanut for example - as being harmful. Having once identified it as being harmful, that is how it remembers it so that any subsequent contact with that substance (now seen as an antigen) will immediately trigger a defensive reaction (allergic symptoms) even though the substance itself is not going to do the immune system or its owner any harm.
Why the immune system should do this remains a matter of speculation.

The defensive reaction

Lymphocytes
Lymphocytes are a type of white blood cell which can recognise an antigen. When they do so they either produce large quantities of antibodies (see below), instruct the immune system how to react, or kill off cells which have been
affected by the antigen.

The ALCAT test which has been around for some 20 years,
assesses changes in the size of the patient’s lymphocytes (white blood cells) when they are brought into contact, in laboratory conditions, with individual foods, chemicals etc, thus, it claims identifying the substance which is causing the reaction.
The programme suggests nutritionally balanced dietary
restrictions (excluding the problem food) which seem to have the added benefit of weight loss for some patients.
The ALCAT test does not find favour in many medical circles but is widely used in both US and the UK.
Costs range from £50 for testing 10 moulds to £199 for 100 foods.www.alcat.info 01638 665 350

First Published 2007

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