The medical controversy about adverse reactions to food is compounded by a long-running dispute over the meaning of allergy. For a word that is scarcely more than 80 years old, it has had a very chequered career. A Viennese doctor, Baron Clemens von Pirquet, first used it in 1906 to mean ‘altered reactivity’. Von Pirquet was a paediatrician and he felt the need for a new medical term to describe certain reactions in his young patients. These changed reactions included the development of immunity to infection, on the one hand, and marked reactions to certain foods, pollen or insect stings, on the other. He was principally concerned with reactions involving the immune system, the set of cells that protect our bodies from infection. But he apparently intended his newly coined word to mean any altered response to the environment. In this context, environment means all the external things that can affect the body, whether in food or water, in the air we breathe, or in things that come into contact with our skin. Von Pirquet also introduced the word allergen to describe the substances that brought about these changed reactions.
At that stage, very little was known about how some of these reactions might arise. The following decades brought greater understanding, and the meaning of allergies was narrowed down – the development of immunity to disease was dropped from the definition, because it was obviously something quite different from adverse reactions to food, pollen or bee stings.
In 1925, the definition of allergy was narrowed down still further. Experiments had shown that many adverse reactions to pollen or food could be transferred from one person to another by injecting a small amount of blood serum into the skin. The area around the injection site became very sensitive to the allergen. This, and other evidence, indicated that the immune system really was at work in these cases, as von Pirquet seems to have suspected. Most of those working in the field decided to limit the definition.
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