The prevalance of asthma an allergy, defined as immunologically mediated hypersensitivity, is increasing. It is estimated that over 20% of the world population suffers from IgE-mediated allergic disease, such as allergic asthma, allergic rhinitis and allergic conjunctivitis, atopic eczema/atopic dermatitis, and anaphylaxis. Asthma, which in more than 50% of adults and in at least 80% of affected children is allergic, occurs in around 5-15% in the paediatric population. Asthma it estimated by the World Health Organization (WHO) to affect about 150 million people worldwide, placing an enormous strain on health resources in many countries, and is a major cause of hospitalizations for chronic diseases in children in the western wolrd. Information may be derived from areas where a rapid increase in disease has occured, to from the basis for prevention strategies in areas where the prevalence of these diseases is still low. Where current expert opinion is still divided, where future research is required, or studies have provided negative results, the available information may prevent the implementation of unnecessary, restrictive, and costly avoidance strategies.