Food allergy in childhood is a popular subject which has attracted disapprobation from certain quarters because of overinflated claims based on flimsy evidence. In this article food intolerance and allergy are defined and the pathogenesis of food allergic reactions is considered. There is a description of the role that food allergy may play in urticaria, angioedema, anaphylaxis, eczema, asthma, rhinitis, cow's milk sensitive enteropathy, infantile colitis, inflammatory bowel disease, migraine and hyperactivity. Factitious food allergy is discussed and the general unhelpfulness of 'allergy testing' commented upon. Finally there is a description of the use of various exclusion diets in the diagnosis and treatment of food allergic disorders. It is concluded that food allergy is important in an increasing number of childhood diseases, but it is not clear what proportion of children with a given condition will respond to dietary measures. The importance of ensuring that exclusion diets are nutritionally adequate is stressed, and there is a plea to remember that an exclusion diet might be worse than the disease itself.