INTRODUCTION: Children living in rural areas had lower prevalence of allergies than children from cities, in relation to farming exposure. STATE OF ART: Exposure to farm animals and consumption of raw milk appear to play an important role in the protection afforded by the agricultural environment, and this at different stages of child development. The mechanisms involved in these effects are still controversial, and recent publications cast doubt on the role of endotoxins initially suggested. It seems that exposure to indoor air pollution, characterized by excessive biocontaminants (mold, allergens...) is a key element in the development of allergic diseases. PERSPECTIVES: The establishment of cohort studies, a better assessment of exposure to pollution at home but also in farm buildings and the study of gene-environment interactions should improve the knowledge on the protective effect towards allergy of farming environment. CONCLUSIONS: The farming environment, very specific, could be an important model for better understanding the mechanisms involved in allergic and respiratory diseases. In addition, urbanization and thus reduction of the rural environment, may well explain the increased prevalence of allergies observed in the past 50 years.