Prevalence of allergic rhinitis and atopic dermatitis among children in four regions of Finland

The primary aim of the study was to evaluate the prevalences of allergic rhinitis and atopic dermatitis and their regional differences among Finnish children. The secondary objective was to determine whether the responses to the questions used are affected by the pollen season if asked during such a season. In 1994-5, the self-reported prevalence of allergic symptoms in four regions of Finland was studied among 11607 schoolchildren aged 13-14 years, as part of the International Study of Asthma and Allergies in Childhood (ISAAC). The prevalence of rhinoconjunctivitis during the preceding year was 16% in eastern Finland (Kuopio County, n=2821), 23% in southern Finland (Helsinki area, n=2771), 15% in southwestern Finland (Turku and Pori County, n=2983), and 16% in northern Finland (Lapland, n=3032). The respective prevalences of flexural dermatitis were 15%, 19%, 16%, and 18%. The surveys were performed in winter, except in the Helsinki area where the survey was carried out mainly in the spring pollen season. Among the children studied in autumn in Helsinki, the prevalence of rhinoconjunctivitis was 19% and that of flexural dermatitis 17%. In multivariate analysis, flexural dermatitis was slightly more common in Lapland than in all other areas. In contrast, no significant differences were found in rhinoconjunctivitis. The prevalences of both disorders were twice as high in girls as in boys. In conclusion, regional differences in the prevalence of allergic rhinitis and atopic dermatitis were small in our country, and the prevalence figures were rather similar to those reported from other European countries. Almost half of the children had suffered from at least one atopic disorder, and over one-third had had symptoms in the past year. A clear season-of-response effect was observed; the prevalence of rhinoconjunctivitis was 25% when studied during the pollen seasons in the Helsinki area.