British Nutrition Foundation
Introduction
Currently, there is considerable confusion about the terminology used to describe various adverse reactions to food. For example, allergy should be reserved for reactions that involve the immune system. In reality these affect relatively few people but can be quite severe. The current estimate for the prevalence of food allergy in the UK is that it affects 1.4% (one to two people in 100) of the population. On the other hand 20% (1 in 5) of the adult population believe themselves to be allergic to a food, although tests fail to confirm that this is the case.
Food allergy most often affects young children, but the majority outgrow this before they go to school. It is important to recognise that, in babies and young children in particular, development of specific antibodies to environmental allergens, especially those encountered in early life, is a normal physiological response via which tolerance to the environment is developed.
Adverse Reaction To Food
The term ‘adverse reactions to food’ can be used as an umbrella term to cover food aversion, food intolerance and food poisoning.
Food aversion: Food avoidance and psychological intolerance
Food intolerance: Allergy, enzyme defect, pharmacological reaction, irritant/toxic
Food poisoning: Bacteria and viruses, moulds, chemicals, toxic foods
Allergy
An allergy is a specific form of intolerance involving the abnormal reaction of a person’s immune system to a substance, e.g. a pollen grain or food constituent, which would have no harmful effect in the majority of people. The immune system protects the body from harmful foreign proteins, antigens, by generating a response to eliminate them. An immune response can involve various cell types and a variety of proteins that can trigger inflammatory reactions. An antibody may be produced against an antigen. An antibody is a protein (an immunoglobulin) that specifically binds with the antigen to deactivate and eliminate it. A person can only display an allergic reaction to a substance after being sensitized to it through initial exposure.
The location within the body of signs and symptoms of food allergy are variable, and they also vary in their timing and severity.
Genetic predisposition and a susceptible immune system, notably elevated blood levels of immunoglobulin E (IgE), are the most important determinants of allergic disease. Exposure to environmental factors, including diet, are secondary to these. Children with high blood IgE levels often suffer from asthma and hayfever and may also be allergic to one or more of the following: cows’ milk, soya, eggs, citrus fruit, or fish.
As mentioned previously, the prevalence of food allergy in the UK at present is estimated to be 1.4% of the population. This figure has been confirmed by double-blind, placebo-controlled food challenges. However, the perceived incidence among adults is over 20%. The prevalence is at its highest in young children, at 5-7% (5-7 children out of 100), although 80-90% of sufferers have outgrown their sensitivity by the age of three years. Children are likely to outgrow an allergy to milk or eggs, particularly if it is not IgE mediated, but are less likely to outgrow allergy to peanuts and fish.
More detail can be found at The British Nutrition Foundation