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FOOD ALLERGY DEFINITIONS: A BATTLE OF WORDS

‘When I use a word it means just what I choose it to mean…’ as Humpty Dumpty declared in Lewis Carroll’s Through the Looking Glass. This sort of verbal anarchy should not be encouraged, but there is so little agreement over terms such as ‘food allergy’, ‘food intolerance’, and ‘food sensitivity’, (not to mention ‘food idiosyncrasy’, ‘false food allergy’, ‘pseudo-food allergy’ and ‘food hypersensitivity’) that anyone writing about this subject is forced to take Humpty Dumpty’s line. There is no option but to select a set of suitable words and state clearly at the outset what is meant by them.

Food allergy is used to mean any adverse reaction to food in which the immune system is demonstrably involved. A positive skin-prick test, as described above, is usually taken as adequate proof of immune-system involvement, although this should be backed up by RAST or other laboratory tests, where possible. Where skin-prick tests or RAST results are negative, this does not necessarily mean that the immune system is not involved. Although reactions involving IgE are the principal cause of such allergies, there are other possible mechanisms, some of which will be considered in Chapter Five. Different kinds of tests are needed for this type of allergy.

False food allergy here denotes a special type of non-immunological reaction, seen with particular foods, in which a substance in the food triggers the mast cells directly. The reaction is not really an allergy at all: the immune system is not at fault and the body does not over-produce IgE. But because the end result (the mast cells releasing their chemical messengers) is the same, the symptoms are exactly like those of food allergy.

Food intolerance, as used in this book, means any adverse reaction to food, other than false food allergy, in which the involvement of the immune system is unproven because skin-prick tests and other tests for allergy are negative. This does not exclude the possibility of immune reactions being involved in some way, but they are unlikely to be the major factor producing the symptoms.

Food sensitivity is employed as an umbrella term for food allergy, food intolerance and other adverse reactions to food, except where these are purely psychological in origin. As will become obvious, the dividing line be¬tween food allergy and food intolerance is sometimes blurred, so there is a need for a term that covers both.

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