Dust from Amish homes in Indiana provides protection against asthma, scientists claim to have proved in research that offers hope of a new kind of treatment.

Previous research has shown that growing up on a farm seems to reduce the chance of getting asthma.

A team of researchers decided to investigate why Amish children had such low rates of the debilitating condition, compared to the children of Hutterites, who live a similar lifestyle.

Only about 5 per cent of Amish children aged six to 14 have asthma, about half the average in the US, while the rate among Hutterites is about 20 per cent.

Both communities were founded by immigrants from central Europe and have similar genetic ancestry, lifestyle and customs.

However, while the Amish still live mainly on single-family dairy farms and use horses, the Hutterites live on large farms that use modern machinery, so their children do not have the same daily exposure to farm animals.

The researchers tested the blood of children from both groups and found the Amish had higher levels of one type of immune-system cell, which fights infections, and lower levels of another that promote inflammation.

They also examined dust taken from the air in Amish and Hutterite homes. When mice were exposed to Amish house dust, they appeared to gain a “significant” level of protection against allergies, but the Hutterite dust did not have the same effect. The Amish dust was also found to be “much richer in microbial products”.

One of the researchers, Professor Carole Ober, chair of human genetics at Chicago University, described the differences between asthma rates among Amish and Hutterite children as a “whopping disparity”.

“Neither the Amish nor the Hutterites have dirty homes. Both are tidy. The Amish barns, however, are much closer to their homes. Their children run in and out of them, often barefoot, all day long,” she said.

“There's no obvious dirt in the Amish homes, no lapse of cleanliness. It's just in the air, and in the dust.

“You can’t put a cow in every family’s house, but we may be able to protect children from asthma by finding a way to re-create the time-tested Amish experience.”

A paper about the research in the New England Journal of Medicine concluded that the results of the study “indicate that the Amish environment provides protection against asthma by engaging and shaping the innate immune response”.

And Professor Donata Vercelli, associate director of the Asthma and Airway Disease Research Centre at Arizona University, added: “The results of the mouse experiments conclusively prove that products from the Amish environment are sufficient to confer protection from asthma.”

Writing in an editorial in the journal, Talal Chatila, a professor of paediatrics at Harvard Medical School, who was not involved in the study, said the “marked increase” in asthma over the past few decades reflected changes in living conditions “associated with modern lifestyles”.

“Overall, the results of the study are consistent with the idea that the protective effect of Amish dust is related to its distinct microbial composition,” he said.

“Long-term, low-level activation of innate immune cells and possibly T-cell–related immune regulatory mechanisms may contribute to the protective effects of the Amish farm dust against asthma.”

However, Professor Chatila added that the study also left “several questions unanswered”.

“It is unclear whether continuous exposure to farm dust is required to maintain its protective effect against allergic asthma,” he said.