Why do farm children tend to avoid asthma and allergies?

Why do farm children tend to avoid asthma and allergies? By Karl Hille The Baltimore Sun August 14, 2026 - 6:00 am German scientists identified bacteria associated with cattle digestion and manure that appear to help children exposed to them avoid developing asthma. The drawback is that children must inhale the germs. As rates of allergies, asthma, eczema and hay fever rose in modern societies, children raised on farms did not seem to be affected. By the 1990s, research suggested that certain childhood infections helped the immune system learn to tolerate rather than overreact to dust, pollen and other allergens. This became known as the “hygiene hypothesis”—the idea that being too clean carries a cost. Now, researchers at LMU University Hospital and the Institute of Asthma and Allergy Prevention at Helmholtz Munich in Germany measured the bacteria that children tend to inhale while playing or working in cattle barns and traced the mechanism that helps combat inflammation in their lungs. “Girls and boys who turn up connected farms and are exposed to a wider assortment of microbes person the occupation acold little often,” epidemiologist Markus Ege said successful a quality release. “With our caller study, we tin marque a overmuch stronger case, due to the fact that we tin place the idiosyncratic links successful the projected causal chain: the bacteria, the applicable microbial metabolic products, and the quality receptors.” The team analyzed data from more than 1,000 children participating in European health studies in rural areas. They compared nasal swabs and samples of mattress dust, as well as airborne samples from cowsheds, for 47 farm children. They published their findings in the July 28 issue of the New England Journal of Medicine. Within the microbial mix of a farm environment, his team’s survey identified nine gram‑positive bacterial genera. Together, those microbes explained two‑thirds of the link between farm exposure and reduced asthma rates. The findings ruled out fungus as a contributing factor. Those bacteria produce chemicals that can act on specific proteins in the human body to help regulate the immune system and inflammation. These chemicals include kynurenine and xanthine, which activate a molecule called the aryl hydrocarbon receptor, and alpha‑linolenic acid and stearidonic acid, two types of stable fatty acids that activate a different molecule called PPAR‑gamma. Both receptors are present on human airway cells. High levels of stimulation are harmful, the researchers wrote, whereas moderate levels indicating only small amounts of time spent in cowsheds appeared beneficial. The effect of the cattle bacteria does not benefit everyone. Small genetic variations, particularly in genes involved in sensing molecules produced by the body or influenced by the gut microbiome, could alter the outcome. The effect is strong enough, Ege said, to suggest new medical treatments to prevent asthma in children who lack access to cowsheds.