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What are Food Allergies?

1. Definitions and Classification

Food Allergies

Food hypersensitivity is the non-specific term which refers to any adverse (untoward) reaction to food or food additives. Food allergy is a type of food hypersensitivity in which the body's immune (defence) system is directly involved and overreacts to a particular protein in that food. There are several types of hypersensitivity reactions to food which are non-allergic, commonly known as food intolerances (a non-immune food reaction).

Food Allergy Reation Diagram

Many people who think they are allergic to a food may actually be intolerant to it. Some of the symptoms of food intolerance and food allergy are similar, but the differences between the two are very important. Food allergy reactions can be life-threatening, in some cases even in response to tiny amounts of the food, so people with this type of allergy must be very careful to avoid their food triggers. Food intolerances are not life threatening and the person may often tolerate small amounts of the triggering food, and have symptoms only on intake of larger amounts.

2. How common is true food allergy?

True food allergy is less common than is popularly believed. Although up to 20-30% of people believe at some sta

ge of their lives that they have a food allergy, it is estimated that only between 2% and 5% of the general population suffers from a definite food allergy. Food allergy can strike children and adults alike. While many children outgrow a food allergy, it is also possible for adults to develop allergies to particular foods.

Food allergy tends to be more common in children (up to 10%) than adults, and several food allergies such as milk and egg allergy tend to be outgrown. In selected groups, such as children with eczema, the prevalence of food allergy may be as high as 30-40%.    

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 This article has been co-written with Paediatrician and Allergy Specialist, Dr Claudia Gray (MBChB (UCT), MRCPCH (London), MScClin Pharm(Surrey), DipPaedNutrition (UK), PostgradDipAllergy (Southampton), Certified Paediatric Allergologist (SA))

Dr Gray works at the allergy clinic at the Red Cross Children's Hospital in Cape Town, and has a private practice at Vincent Pallotti Hospital in Cape Town, contact 021 531 8013.