The clinical interpretation of children sensitized to numerous allergens is challenging. We examined differences between children sensitized to zero, one, or more allergens. This was a retrospective analysis of all specific IgE tests in children 0-18 yrs of age sent to our laboratory by general practitioners and hospital-based specialists for allergy testing between 1990 and 2003. Of all 9044 children tested, 5439 (60.1%) were not sensitized to any of the aeroallergens or food allergens tested. Three thousand six hundred and five children (39.9%) had one or more positive specific IgE tests, 1120 of which (31.1%) were monosensitized (73% to aeroallergens and 27% to food allergens), 1709 (47.4%) were sensitized to two to four allergens, and 776 (21.5%) to five or more allergens (polysensitization). Polysensitization was more common in children 4-11 yrs of age (24.8%) than in younger (18.7%) or older children (18.3%, p < 0.001), and more common in boys (9.8%) than in girls (7.3%, p < 0.001). Median total IgE values increased with increasing number of positive specific IgE tests (p < 0.001). House dust mite more commonly showed monosensitization (22.2%) than other aeroallergens (grass pollen 10.5%, tree pollen 3.6%, cat 2.9%, and dog 1.5%); cow's milk (27.6%) more commonly than other food allergens (hen's egg 9.7%, peanut 4.6%, wheat 0.8%, soy 0.7%). Between 55.7% (cow's milk) and 87.9% (soy) of children sensitized to food were cosensitized to aeroallergens, while only 25.4% (house dust mite) to 39.5% (dog) of children sensitized to aeroallergens were cosensitized to food. Polysensitization is common in children, in particular in boys. It is most common in school-aged children. The strong association with total serum IgE values and the striking cosensitization between biologically unrelated allergens suggest that polysensitization is the expression of a distinct clinical, more severe, atopic phenotype, and not of biologic cross-reactivity to similar allergens.
© 2010 John Wiley & Sons A/S.