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Food allergies and intolerances
Edited by Dr Mabel Blades
Introduction
The range of symptoms associated with adverse reactions to food (food hypersensitivity) is wide and includes itching, eczema, urticaria, angioedema, asthma, rhinitis, intestinal symptoms and headache ([42] Zuberbier et al. , 2004). Reported prevalence of food hypersensitivity varies widely from 3 to 35 per cent (reviewed in [26] Madsen, 2005), with others claiming higher rates up to 45 per cent (Allergy UK Report, 2007). There are several proposed mechanisms by which an individual may have an adverse reaction to food. According to a recent review of nomenclature, food hypersensitivity may be either allergic or non-allergic, the latter including adverse reactions due to enzyme deficiencies and pharmacologically active food components ([23] Johansson et al. , 2004; Figure 1 [Figure omitted. See Article Image.]). Food allergy refers to cases where immunological mechanisms are demonstrated and includes IgE- and non-IgE-mediated allergy.
The current gold standard approach for confirming non-IgE-mediated allergy, is to follow an elimination diet, excluding all except a few foods, for a few days to a few weeks. Once the symptoms are controlled, this is followed by challenge with foods one at a time (preferably double-blind, placebo-controlled challenge) to identify the offending foods. The clinical usefulness of this approach is limited by the fact that it is very expensive, lengthy and requires a high level of patient compliance ([6] Bruijnzeel-Koomen et al. , 1995). Furthermore, it may give rise to false negative challenges, for example due to an insufficient dose of challenge food, insufficient duration of challenge, or long lag times post-challenge before symptom exacerbation ([15] Freed, 2002). It is also clear that it is well nigh impossible to test all the different combinations of food types that may be causing the problems. Hence there is a need for more simple tests to make the identification of offending foods in patients with non-IgE-mediated food allergy more feasible in clinical practice. In addition, it has also been suggested that patients may be more compliant to a diet based on the results of a laboratory test as it may be considered to be more "scientific" ([40] Zar et al. , 2005a).
It has been proposed that food-specific IgG antibodies play a role in the underlying mechanism of non-IgE-mediated...