Chapter 194

Food allergies, defined as adverse immune responses to food proteins, are an increasingly common concern in the pediatric age group. Food allergy is not one disease, but a spectrum of clinicopathological disorders.1 As such, its manifestations differ significantly, depending on the immune mechanism involved and the affected target organ, ranging from the prototypical acute urticaria/angioedema to chronic conditions such as eczema or failure to thrive. Currently, there are no tests that can reliably predict the severity of a food allergic reaction, which may vary with similar exposures and even in the same individual. As a whole, fatalities are rare, but they do occur. Teenagers are particularly vulnerable because they undertake unnecessary risks and may ignore the warning signs of an impending severe reaction.

Because a diagnosis of food allergy entails a considerable nutritional and social burden for the affected children and their families, all efforts should be geared to ensure that a true food hypersensitivity is the cause of the patient’s complaints. This is not an easy task, given the protean clinical manifestations of these disorders and the recognized pitfalls of the routine laboratory tests. In some instances, a double-blind placebo controlled food challenge (DBPCFC) may be necessary. This costly and at times cumbersome procedure is at present the only gold standard for the diagnosis of food allergy.

Food allergies are often the first step in what has been termed the atopic march, involving the sequential development of different allergic diseases in the same child.2 While many children will outgrow their food allergies before their sixth birthday, for others this will remain a lifelong concern. For the vast majority of food hypersensitivities, there are presently no curative treatments. Current management of these conditions relies on careful avoidance of the offending food(s) and initiating therapy to curtail symptoms in case of accidental exposures. Yet, reinstructing the immune system to tolerate food allergens is an attainable goal, as demonstrated by the success of allergen-specific immunotherapy in the treatment of respiratory allergies. Growing evidence from a number of clinical trials suggests that the same can be achieved in food-allergic patients, which could radically change the way in which these patients are managed in the near future.3

Food allergies are far more prevalent in developed countries than in the developing world. In the United States, the overall prevalence of food allergy has been estimated in 3.5% of the general population, with roughly twice as many children than adults afflicted by these disorders.4 Like other allergic diseases, food allergies appear to be on the rise. The prevalence of peanut allergy, for instance, has more than doubled in the last 10 years, both in the United States and in Great Britain.5 The interaction of genetic, dietary, and environmental factors appears central to the recent increase in food allergies.

Food allergies have a strong genetic component. Studies in twins show that 7% of dizygotic and 64% of monozygotic twins share a peanut allergy, and siblings from a peanut-allergic ...

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