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Background Atopic allergy has been more common among schoolchildren in Finland, as compared to Russian Karelia. These adjacent regions show one of the most contrasting socio-economical differences in the world. Objective We explored changes in allergy from school age to young adulthood from 2003 to 2010/2012 in these two areas. The skin and nasal microbiota were also compared. Methods Randomly selected children from Finnish ( n = 98) and Russian Karelia ( n = 82) were examined in 2003, when the children were 7-11 years of age, and again in 2010 (Finnish Karelia) and 2012 (Russian Karelia). We analysed self-reported allergy symptoms and sensitization to common allergens by serum sIgE values. The skin (volar forearm) and nasal mucosa microbiota, collected in 2012 (aged 15-20 years), identified from DNA samples, were compared with multivariate methods. Results Asthma, hay fever, atopic eczema, self-reported rhinitis, as well as atopic sensitization, were threefold to 10-fold more common in Finland, as compared to Russian Karelia. Hay fever and peanut sensitization were almost non-existent in Russia. These patterns remained throughout the 10-year follow-up. Skin microbiota, as well as bacterial and fungal communities in nasal mucosa, was contrastingly different between the populations, best characterized by the diversity and abundance of genus Acinetobacter; more abundant and diverse in Russia. Overall, diversity was significantly higher among Russian subjects ( Pskin < 0.0001, Pnasal-bacteria < 0.0001 and Pnasal-fungi < 0.01). Allergic diseases were not associated with microbial diversity in Finnish subjects. Conclusions and Clinical Relevance Differences in allergic phenotype, developed in early life, remain between populations. A parallel difference in the composition of skin and nasal microbiota suggests a potential underlying mechanism. Our results also suggest that high abundance and diversity of Acinetobacter might contribute to the low allergy prevalence in Russia. Implications of early-life exposure to Acinetobacter should be further investigated. [ABSTRACT FROM AUTHOR]

Background and aim: The influence of microbial quality of drinking water from different sources on the occurrence of atopy has been poorly examined. This study was undertaken to clarify the association between the overall microbial content in drinking water and the occurrence of atopy among schoolchildren from two neighbouring areas with profound differences in living conditions and lifestyles. Methods: Drinking water samples were obtained from kitchens of nine schools in North Karelia, Finland and of nine schools from Pitkäranta, the Republic of Karelia, Russia. The pupils of these schools were participants of the Karelian Allergy Study. Occurrence of atopy, determined by skin prick test positivity (one or more) to 14 common airborne and food allergens, was measured in all 563 children, aged 7–16 years, from these 18 schools. Water samples were analysed using standard methods for drinking water analyses including viable counts for Escherichia coli, intestinal enterococci, coliform bacteria and heterotrophic bacteria. In addition, total cell counts including both viable and nonviable bacteria, algae and protozoans were assessed using epifluorescence microscope with 4′-6-diamidino-2-phenylindole (DAPI) staining. Results: In Finland, 29% of the children were sensitized to birch when compared with 2% of the Russian children ( P < 0.0001). Overall, sensitization rates for any of the pollens were 39% and 8% ( P < 0.0001), and for any of the allergens 48% and 16%, respectively ( P < 0.0001). Because of substantial differences in raw water sources and treatment practices, the total numbers of microbial cells in drinking water were many-fold higher in Russia than in Finland. A dose–response relationship was found for occurrence of atopy and the DAPI value indicative of microbial cell content in the water ( P < 0.0001). Further, multivariate logistic regression analysis revealed that high (>106 cells/ml) and intermediate (105–106 cells/ml) DAPI values were associated with reduced risk of atopy (odds ratio 0.34, 95% confidence interval 0.20–0.57 and 0.39, 0.23–0.69, respectively), independently from other factors. Conclusion: High overall content of micro-organisms in drinking water may be associated with reduced risk of atopy, independently from other determinants. [ABSTRACT FROM AUTHOR]