Children who grow up in a farm environment are less prone to allergies, asthma, and hay fever than their classmates. This so-called farm effect has been identified in several observational studies worldwide. It is most likely attributable to the fact that various bacteria present in barn air prevent excessive inflammatory responses of the immune system that are characteristic of such diseases. But which bacteria exactly?
An international team led by Professor Markus Ege from the Dr. von Hauner Children’s Hospital at LMU University Hospital and the Institute of Asthma and Allergy Prevention at Helmholtz Munich has answered this question. The researchers have shown for the first time which specific bacteria in barn air trigger the farm effect, which substances within those bacteria mediate the protection, and which receptors in the body they bind to. Their findings have been published in The New England Journal of Medicine – Evidence.
Microbes protecting from Asthma and Allergies - How were they discovered?
The researchers analyzed data from more than 1,000 children participating in European studies in rural areas. For all the children, girls and boys, two types of samples had been collected: nasal swabs and mattress dust. In addition, dust samples were taken from cowsheds for 47 farm children. The team examined which bacteria and fungi were present in these samples, how the different microorganisms were related, and whether specific microbial groups protected the children against asthma.
The researchers identified bacterial species such as "Romboutsia timonensis" and "Glutamicibacter arilaitensis", which account for a substantial part of the protective farm effect. They also uncovered the human receptors involved, providing the strongest evidence to date for how environmental microbes help shape immune health.
From Cows to Asthma Prevention—How Does It Work?
“These receptors,” Ege continues, “have multiple functions, including in the immune system, where they appear to prevent excessive inflammatory responses.” Their role in the farm effect was previously unknown. For the first time, therefore, the complete biological chain is visible: cow → barn air → bacteria → metabolic products → human receptors → protection against asthma.
The new findings can now be used by laboratory researchers to decipher the molecular and cellular mechanisms of the farm effect. This opens up the prospect of developing a drug that mimics the farm effect – without the need for children to spend time in barns.
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