Most surveys that have used similar methodologies to measure changes in the prevalence of wheezing and asthma in western, affluent countries report significant increases in the prevalence of childhood asthma for the last decades . In most of these studies, prevalences were assessed by responses to questionnaires. Some included objective measures of factors known to be associated strongly with asthma such as airway hyperresponsiveness and atopic sensitization. Most also acknowledged that an increased awareness of allergic diseases by physicians and parents, and changes in diagnostic habits may have accounted, at least in part, for the rising trends .
Atopic dermatitis (synonym: atopic eczema) is a chronic or chronically relapsing, inflammatory skin disease with a spectrum of characteristic clinical features and with altered immunological and pharmacological responses. Wise and Sulzberger  who proposed the terra atopic dermatitis (previous name neurodermatitis, prurigo diathésique, prurigo Besnier) recognized its frequent association with extrinsic asthma and allergic rhinitis.
Although frequently suspected, food hypersensitivities occur in only 2 to 5% of the general population. These occur because food processed in the gut escapes immunoregulatory mechanisms that usually effectively prevent these reactions from developing. When they fail, hypersensitivity, which may be either IgE- or non-IgE-mediated results. Although the events that lead to these reactions are initially in the gut, patients may experience multisystemic symptoms (e.g. anaphylaxie). Or, symptoms may be more focused affecting only the skin (e.g. urticaria/angioedema and atopic dermatitis) or the respiratory tract (e.g. upper or lower airway symptoms). Non-IgE-mediated reactions most often involve the gastrointestinal tract. Most commonly, infants suffer from enterocolitis, milk-induced colitis, or food-induced enteropathy, and older children are most likely to experience allergie eosinophilic gastroenteritis.
Atopic diseases affect almost 33% of the population and constitute a major public health problem. The prevalence of atopic dermatitis, asthma and other atopic respiratory manifestations has dramatically increased during the last decade . The significance of the increased incidence of atopic disorders is heightened by the dramatic rise of the health care costs induced by allergic diseases, and the lower cost-benefit ratio of prevention than treatment for the society, the family and the patients [2, 3].
The prevalence of atopy in childhood has increased considerably over the last decades. This increased prevalence is of great concern to paediatricians and epidemiologists. Although the affluent western life style is clearly associated closely with this rise in childhood atopy, its immunological mechanisms, genetic basis and environmental factors that trigger atopic disease in childhood remain topics of intense investigation. The increased prevalence of sensitization to airborne allergens parallels that of other atopic conditions such as atopic dermatitis. Better hygiene and less infectious diseases in affluent populations are associated with higher rates of atopy. Thus improvements in the general health of populations paradoxically are associated with the exacerbation of some conditions. The overall prevalence of atopic disease in childhood reaches 20% of children in affluent societies whereas, in less affluent countries, the prevalence is 2,6 to 6% .