Rural Children Have Fewer Allergies

Children who grow up with ample exposure to a variety of microorganisms gain protection from conditions like childhood asthma. Children living on farms were compared with those who were not for conditions like allergies and asthma, as well as the range of microbes they were exposed to. Dust from their mattresses was analyzed for bacterial DNA, while cultures from dust settled in their rooms were analyzed for bacterial and fungal presence. “In both studies, children who lived on farms had lower prevalence of asthma and atopy (tendency to develop allergic sensitivity) and were exposed to a greater variety of environmental microorganisms than the children in the reference group.”

The more the exposure to environmental microbes, the lesser are the chances of getting allergies and asthma. Studies conducted mainly in Europe have shown that children living on traditional farms rarely suffer from hay fever. This study looks for markers for exposure to a wide range of microbes based on a large-scale analysis of schoolchildren living in the same rural area in Europe, some of whom partly lived on farms. The range of microbes they were exposed to was correlated to the range of conditions like asthma that were observed among these children. Techniques for determining the microbes included single-stranded DNA polymorphism to detect the range of microbes in the environment, in addition to cell culture studies.


  • The study used two populations of students who did or did not live on farms in rural and suburban areas in central Europe.
  • Two techniques were used to determine the microbes present in their environments: the PARCIFAL study used single-stranded DNA polymorphism of bacteria from dust samples collected from mattresses.
  • The GABRIELA study used dust settled in the children’s rooms to create cultures on plates. The resulting colonies of fungi and bacteria were further categorized according to standard microbiological staining methods.
  • Blood was also tested for exposure markers like antibodies. Questionnaires were used to determine the symptoms of respiratory conditions and exposure, age etc.


  • Fewer asthma cases were seen among children living on farms than those who were not. The difference was greater for allergies, which were common among non-farm-dwellers. The reported asthma was confirmed by medical tests.
  • Mattresses of children living on farms had more microbial diversity, which suggested more exposure.
  • The risk of asthma decreased as the number of bacterial and fungal species in the environment increased.
  • Exposure to certain types of bacteria and fungi seemed to have an inverse effect on asthma.

Shortcomings/Next steps
The microbes were categorized based on the mobility of their DNA on electrophoresis gels and by using standard microbiological staining methods. These are broad categories, and it is important to identify specific microbes to which the children are exposed. The next step would be to figure out how they provide protection against asthma.

Children living in the same regions showed higher exposure to various microbes if they lived on a farm. The greater the exposure, the higher were the chances of protection from developing asthma. No clear correlation was seen for allergies, although certain fungi seem to provide protection against allergies. The mechanisms for protections against asthma and allergies might be different. Exposure to certain groups of bacterial or fungal species was correlated with farm living and protection from asthma, but no single species stood out. The protection might be due to microbial stimulation of the children’s immune system, which starts recognizing similar patterns in further microbial exposures.

For More Information:
Exposure to Environmental Microorganisms and Childhood Asthma
Publication Journal: The New England Journal of Medicine, February, 2011
By Markus J Ege; Melanie Mayer, PhD
From the University Children’s Hospital Munich, Munich, Germany and Technische Universität
München, Freising, Germany

*FYI Living Lab Reports Are Summaries of the Original Research.

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