CHICAGO (AP) — Research in the Amish and Hutterites sheds new light on asthma. Those farming-based religious groups shun modern ways and are similar genetically. But asthma is uncommon in Amish communities but higher in the other group.

In the new study, blood samples showed Amish kids had more types of white blood cells that help fight infections. Dust samples taken from homes in both groups also offered clues. Lab mice sensitized to develop asthma showed symptoms when exposed to Hutterite dust but not Amish dust.

The researchers think germs from nearby cows may wind up in the dust and somehow protect kids. Hutterites have mechanized farms and their kids have less contact with farm animals.

The study was published in Thursday’s New England Journal of Medicine.