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This study was carried out to evaluate the relationship between wheezing or sensitization and concentrations of mites, cat and dog allergens, and bacterial endotoxin in Palestine. A nested case-control involved analysis of mattress and floor dust from a 110 children's houses with reported wheezing and without wheezing. We found no consistent associations between allergen levels and either wheeze or specific atopic sensitization. Furthermore, no clear associations between mattress endotoxin levels and wheeze or atopy were found. Endotoxin in floor dust was inversely associated with atopic sensitization and wheeze, statistically significant only for atopic wheeze. Finally, a nonsignificant inverse association was observed between living room endotoxin and atopy within the non-wheezing control group. In conclusion, although our study found mostly negative results, it does suggest that endotoxin on living room floors might protect against atopic wheeze. However, this finding should be interpreted with caution due the relatively small sample size of the study and requires further confirmation.

Background: A few studies have compared indoor allergens and endotoxin levels between urban and rural settings as important determinants for asthma and atopy in children. However, no study was done in the Middle East or investigated refugee camps., Methods: As part of a nested case-control study in Ramallah in 2001, we measured house dust mite and pet allergens, as well as endotoxin in dust collected from 110 children's mattresses and living room floors., Results: Geometric mean (GM) concentrations of Dermatophagoides pteronyssinus (Der p1) antigen were 4.48 microg/g in mattress dust and 1.23 microg/g floor dust. The highest Der p1 levels were seen in refugee camps. Concentrations of Dermatophagoides farinae antigen (Der f1) were much lower (<0.08 microg/g dust). Concentrations of cat allergen (Fel d1) were highest in villages, and those of dog allergen (Can f1) were highest in mattresses from cities and in floor dust from refugee camps. GM of endotoxin levels were 25.7 EU/mg in mattress dust and 49 EU/mg dust in floor dust., Conclusions: Concentrations of Der p1 were high compared to Western European countries, but were lower compared to UK and Australia. Levels of pet allergens were lower than in Western Europe. Endotoxin levels were higher compared to developed countries. Indoor environmental factors such as dampness seemed to be important determinants for allergen and endotoxin, but living habits such as lack of mattress cover appeared unimportant.