What makes a child allergic? Analysis of risk factors for allergic sensitization in preschool children from East and West Germany

Earlier epidemiologic studies within Germany found a higher frequency of al lergic sensitization in West Germany. The reasons for that and the role of environmental factors in the process of allergic sensitization are not full y understood. This study aimed to determine the prevalence of positive skir t-prick test results 5 years after unification and to investigate risk fact ors for allergic sensitization in preschool children. A total of 1235 child ren (5-6 years) from two West and five East German locations were skin-pric k rested after the compulsory school entrance examination. Six common aero- (birch, grass, mugwort pollen, cat, HDM, alternaria) and two food allergen s (egg, milk) were used and additional information was obtained by question naire. Of the tested children 23.3% exhibited at least one positive reactio n. The prevalence of sensitization to the single allergens was as follows: grass (14.4%), birch (66%), mugwort pollen (4.5%), cat (8.5%/, HDM (5.5%), altemaria (4.9%), egg (2.8%), and milk (3.9%). In the crude analysis signif icantly more children were sensitized in the East German city Magdeburg (40 .2%) compared to the West German control region Borken (23.5%) (OR 2.20 CI 1.47-3.29). Dampness and visible molds were reported in 8.8% of all househo lds, but significantly more often for East German apartments (10.3% versus West Germany 1.9%, OR 5.85, CI 2.55-16.53). Dampness and molds were associa ted with a higher frequency of sensitizations (40.6% versus 27.6% in unaffe cted homes). After controlling for sex, parental atopy, SES, family size, a nd smoking during pregnancy, this association remained statistically signif icant (OR 1.93, CI 1.19-3.12). With regard to single allergens, dampness an d visible molds were significantly associated with sensitization to HDM (OR 3.37, CI 1.63-6.96), cat (OR 3.19 CI 1.11-5.74), and mugwort pollen (OR 2. 86 CI 1.29-635). In addition, family size was inversely and linearly associ ated with the frequency of sensitization (OR for four, three, and two-perso n households: 1.10 (0.74-1.63), 1.57 (1.06-2.42), 2.70 (1.39-5.24), respect ively when compared to family size of five or morel. Neither parental predi sposition for atopic diseases nor parental education level influenced the p rick test reactivity. We conclude that in addition to genetic predispositio n, environmental factors like indoor climate and probably infectious stimul i (family size) play an important role in the process of allergic sensitiza tion in children.