Decreased markers of atopy in children with presumed early exposure to allergens, unhygienic conditions, and infections.

BACKGROUND: Several risk factors for the development of asthma and atopic disease in children have been described. Furthermore, there is consistent evidence that the prevalence of atopy increases with higher socioeconomic status. The knowledge about risk factors and preventive factors for atopy needs to be improved. OBJECTIVE: To compare 2 child populations (foster care and reference children) with different risk and protective factors for the development of atopy. METHODS: The study group consisted of 415 children, living in all 10 community foster homes in Lodz, a large industrial city in Poland. The study was performed from April 2, 2004, to April 30, 2006. The reference group consisted of 500 children, living with their parents at home, recruited from primary care centers. The primary outcome measures were skin prick test results and specific IgE in serum. Secondary outcomes included symptoms of allergic diseases and family history, including life conditions in early childhood. RESULTS: The full analysis set included 408 study children and 402 reference children. Significant differences were observed in the prevalence of atopy between the study and reference groups (11.3% vs 25.9%). We observed more positive skin prick test results in children from the reference group than in study children. To explain this phenomenon, we selected 16 variables that differ in both groups in early life and relate these to atopy. We found that the more cumulative features characteristic of the foster home population (poor living conditions), the lower the risk of atopy. CONCLUSION: Extremely unfavorable environmental circumstances, which are characteristic of the foster home population during early childhood, might prevent from atopy.