摘要Objective: The aim of this study was to assess school indoor exposure to microbial products and prevalence of asthma and allergies in rural and urban children. Methods: This study was carried on a rural and an urban school. Environmental endotoxin level was measured in multiple samples of the ambient indoor air dust collected on special aseptic filter papers from the two schools. For two hundred children history taking, clinical examination, allergen skin prick test and basic pulmonary function test were preformed. Results: Environmental endotoxin levels showed significantly higher mean values (P<0.01) in rural school (3 EU/mg) as compared to the urban school (0.1 EU/mg) with (OR=5.163; 95% CI: 0.95-28). History of allergic symptoms was significantly more in urban than rural students (P=0.01). Mean values of pulmonary function parameters were significantly lower values in urban students compared to rural students. Skin prick test results showed significant reactions to all tested allergens in urban children compared to rural children (P<0.05). Conclusion: There is an inverse association between environmental exposure to endotoxins and susceptibility for allergic manifestations in school children.