Prick Test for Allergy

Conventional medicine has generally not been successful in the diagnosis and treatment of allergies. Limited success has been achieved with airborne and home-related causes such as pollens, dust, house mites and pets. Because of this; specialists have continued to use similar methods in attempts to detect food and chemical sensitivities. The results have invariably been poor with testing proving to be inaccurate and treatment ineffective.

Why then do doctors persist in using medical techniques that do not do the job? The answer is simple. In this age of the much publicized 'wonder drug', people have come to expect quick diagnosis and treatment. Doctors, as well as patients, have fallen into the convenient trap of looking to drugs and chemicals for prompt results. It is faster and simpler to buy an allergy test kit from a drug manufacturer and use it on a patient, than to persist over a period of time with observation and deduction. If the test kit does not work the doctor explains that he cannot do more until medical science produces a better one. This reliance on manufactured preparations has tended to work against allergy sufferers, and it is only comparatively recently that alternative clinical methods of diagnosis have begun to emerge.

Prick Test:
Extracts of well-known allergens such as pollen, house mite or cat dander, are manufactured by drug companies for use in a variety of tests, to ascertain which substances are allergenic to a specific individual.

A simple test is carried out, by placing a drop of the extract on the skin of the forearm and gently pricking it into the upper layer of skin. Up to twenty, or more, of these pricks, each with a different substance, can be carried out in one visit to the allergist. If you are sensitive to a substance, the spot will swell slightly and become red within about fifteen minutes. This does not mean, however, that you are allergic to that substance, simply that, were you exposed to it often enough, or for long enough, you might become allergic to it. It could also mean that you were once allergic to it but, for some reason, are no longer. Even a positive result is far from conclusive and, at best, gives a vague indication only. Nevertheless, this form of testing has had some success in diagnosis and treatment of the airborne, or household, type of allergy. It is also quite often used to test for food allergies and, for this purpose, it is totally unreliable.

Because allergies affect the immune system, it is possible, by examining its structure, to see why skin tests do not detect food and chemical allergies. Made of antibodies which the immune system manufactures in order to destroy antigens. These antibodies are known medically as 'immunoglobulins', of which there are five main types, IgE, IgD, IgG, IgM and IgA.

IgE is bound to mast cells and resides mainly in the skin mucosa, where it is responsible for contact reactions and allergic manifestations, such as urticaria. In the case of an allergy reaction, the IgE, when confronted with an antigen such as pollen, does not destroy it. Instead, the antigen causes the mast cell, to which the IgE is attached, to break up and release a flood of histamine, which in turn gives rise to the allergy symptoms. IgD is thought to initiate IgE production. IgG and IgM antibodies are found mainly in the blood. It is their job to travel the body and ward off infection by dealing swiftly with invading antigens such as foreign bacteria. In addition IgM acts as a rallying point for a number of IgGs to bind together and form a stronger defence mechanism.

IgA is found mainly in the gut and is produced by the gastro­intestinal cells. It acts in a similar way to IgG and IgM, but, instead of patrolling the body, it remains in situ in the stomach and intestine. There, it is ready to attack harmful substances brought in to the body by the process of eating and drinking.

Skin testing, therefore, is likely to stimulate only the IgE system. The systems most likely to be involved with food and ingested chemicals, namely the IgG, IgM and IgA systems, cannot be reached through skin testing. Consequently, skin testing can stimulate the IgE system to produce an allergic response to pollens and house mites, but will fail to stimulate other antibodies to react to food substances.

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