Children who grow up on farms have a lower prevalence of allergies and asthma than other children in the same geographical region who do not grow up in such environments. Is the wider range of microbes in their environment the main reason why they are better protected against the development of allergy and asthma? A study by a European group of researchers published in the renowned New England Journal of Medicine adds to evidence supporting the “hygiene hypothesis”. One of the authors, Jon Genuneit, works at the Institute of Epidemiology and Biometrics at the University of Ulm.
In their study, the researchers were able to link the protective effect of exposure to bacterial taxa. Eurotium, Penicillium, Bacillus and Staphylococcus bacteria have been shown to have an allergy-preventive effect. Genuneit is sure that he and his research colleagues have reached their goal: “We have generated hypotheses, which we will now be able to test in greater detail in future investigations.”
Two European cross-sectional studies (GABRIELA and PARSIFAL) focused on the environmental influences that are thought to contribute to the development of allergies and asthma. “We found that asthma and allergies are the result of genetic factors and environmental influences,” said Genuneit in reference to the bigger picture in which the findings of the European group of researchers must be placed.
There are many reasons, rather than just one single reason, as to why children who grow up on traditional farms are more effectively protected against allergies and asthma than children who do not grow up on farms. The goal of the European team of researchers was to determine the factors that contribute to allergy/asthma protection.The GABRIELA study (Multidisciplinary study to identify the genetic and environmental causes of asthma in the European Community) commenced in 2006, involving around 13,000 of a total of 100,000 primary school children aged six to twelve living in areas that are in close vicinity to the Alps (Bavaria, Baden-Württemberg, Switzerland, Austria, Poland). The epidemiologists grouped farming lifestyle or the contact with farming lifestyle into three categories: children who lived on farms; children who have contact with farms and children without any contact with farms. The volunteers’ parents/legal guardians filled out a questionnaire, and the children’s blood as well as samples of settled dust from children’s rooms were evaluated for bacterial and fungal taxa with the use of culture techniques, microscope and Gram staining.
The New England Journal of Medicine study has raised a new hypothesis on the basis of validated data that children living on farms are exposed to a greater quantity and wider range of microbes and fungi than children in the reference group and that this exposure explains why such children are more effectively protected against asthma and allergies. Genuneit has stated that the researchers will now focus on a more detailed investigation of the microbial taxa that have been identified and look into whether certain species provide a higher degree of protection against the development of allergies and asthma. The epidemiologist went on to add that these investigations do not provide information about the effect of the fungi and bacteria but do nevertheless provide important insights into the fact that exposure to a wider range of potential allergens reduces the risk of asthma and allergy developing.
Literature: Ege, Markus; Meyer, Melanie et. al.: Exposure to Environmental Microorganismus and Childhood Asthma, in: New England Journal of Medicine, 24. Febr. 2011, S. 701-709,Ege, Markus; Strachan, David et al.:Gene-environment interaction for childhood asthma and exposure to farming in Central Europe, Journal of Allergy and Clinical Immunology 2011;127:138-44.) doi:10.1016/j.jaci.2010.09.041)