Allergic disease is a common cause of morbidity, particularly in young children. The prevalence of allergic disease has increased in the last 20 y in most countries. The sequential order of occurrence of allergy is food hypersensitivity, gastrointestinal manifestations, atopic eczema, asthma and hay fever. A variety of factors increase the risk of allergic disease, for example hereditary predisposition, exposure to 'allergenic' foods and environmental triggers such as house dust mites and tobacco in early life. Prolonged breast feeding, the use of a partial whey hydrolysed formula, delayed introduction of certain 'allergenic foods', and avoidance of inhalant allergens reduces the incidence of eczema and asthma, especially in high-risk infants. These preventive measures are extremely cost-effective and should be adopted widely at the community level.