Food allergy and food intolerance in childhood.

Food intolerance is a reproducible adverse reaction to a specific food ingredient that is not psychologically based. Food allergy is a form of food intolerance in which there is evidence that the response is caused by an immunological reaction to food. Other mechanisms of food intolerance include enzyme defects (e.g. lactase deficiency), pharmacological effects (e.g. histamine), toxic properties (e.g. haemagglutinating lectins) and irritants (e.g. spices). Food allergy in children is a highly contentious subject and there is often a striking lack of published evidence from which to base clinical decisions. The true prevalence of food allergy in children is unknown, although there is evidence of an increasing incidence of allergic reactions to some foods, especially peanuts. Our understanding of why some children are unable to tolerate certain foods (e.g. cow's milk, egg), or how they grow out of this intolerance, is very poor. Symptoms of food allergy in children are diverse and include vomiting, poor weight gain, abdominal pain, malabsorption, cough, wheeze, rhinitis, atopic eczema, urticaria and angioedema. Despite the lack of objective data to support the notion that food intolerance contributes to behaviour in children, this is a belief firmly held by many parents and some professionals. The gold standard for diagnosing food intolerance is the double-blind placebo-controlled food challenge (DBPCFC). There is often a poor correlation between the results of food provocation tests and those of skin prick tests of radioallergosorbent tests for specific food antibodies. For proven food allergy, elimination diets are the mainstay of management. In children these must be closely supervised to avoid nutritional deficiency and compromise of growth. Some children who have had severe (anaphylactic) reactions after food need to have a supply of self-injectable adrenaline made available to their parents and teachers and must also practice strict avoidance of the offending food.