Why is the prevalence of allergic diseases increasing? A critical assessment of some classical risk factors.

molecules, is a prerequisite to provoking eczematous lesions, observed after application of aeroallergens to the skin of atopic patients, strongly supports this concept. Thereby, IgE receptors are the connecting link between the specificity gaining IgE molecules and the APC. However, Fc«RI seems to play the major role in these phenomena. It should be noted that Fc«RI expressed on circulating monocytes may have other functions, mainly in regulating their survival and differentiation outcome. Following the presentation of allergens to T cells, allergen-specific B cells may be activated to produce high amounts of allergen-specific IgE. This IgE may then in turn bind to the Fc«RI on the APC, closing a vicious circle of facilitated antigen presentation. The intermittent or continuous supply of aeroallergens or autoantigens to the process of facilitated antigen presentation may define the pathophysiological basis of the recurrent or self-perpetuating course of AD frequently seen in untreated patients. The successful application of aeroallergens such as cat dander in the recently standardized atopy patch test shows that it is possible to elicit eczematous skin lesions by solely external application of aeroallergens to the skin. Based on the facilitated antigen presentation model of AD, the need for an identification of the individual provocation factors in each patient calls for diagnostic procedures based on the allergen-specific IgE. Cat dander, house dust mite allergens and a variety of food allergens may be successfully avoided following a thoroughly undertaken prick test and in vitro IgE diagnostic evaluation.