Atopic allergic diseases have become a public health problem because of the marked increase in their incidence along the second half of the 20th century, and their relationship with environmental changes observed in that period of time. Within the "hygiene hypothesis" which associated this increased incidence with a decrease in children's exposure to microbial agents, cross-sectional studies stressed the relationship between dairy farm specific environments with a significant protection against allergy. For the last 15 years, since the last trimester of their mother's pregnancy until now, in the PASTURE cohort 1000 children have been studied in dairy farming regions of 5 European countries (Austria, Finland, France/Franche-Comte, Germany, and Switzerland); 500 lived on a farm and 500 also lived in rural areas, but did not live on a farm. The results of this multidisciplinary endeavor pointed to the role of (1) the diversity of exposure to animals, microbes, and food in early childhood; (2) the consumption of raw milk and milk products; (3) maternal exposure before delivery for the immunological and allergic future of the child; (4) an early orientation/differentiation of dendritic cells, T cells and secreted cytokines towards a "regulatory profile", under the influence of the environmental factors. The PASTURE cohort is a remarkable example of European cooperation to better understand a public health problem, and of the involvement of families in a very demanding clinical research project. Its coordinators now expect to maintain the follow-up of the children until adult age and to work on "farm-like" preventive measures. (C) 2019 l'Academie nationale de medecine. Published by Elsevier Masson SAS. All rights reserved.