The widespread increase in the prevalence of allergic disease, which has occurred over the last 20 y, has created general concern in Europe and in the rest of the world. The reason for this increase is still partially unknown. In this period, despite a greater understanding of the pathogenesis and risk factors of allergies plus the greater efficacy of drugs to control the symptoms, the cost of intervention and the socio-economic impact are still very high. For these reasons, prevention in the first period of life represents a goal for both developed and developing countries in order to reduce this upward trend.