The Amish who live and work with animals on farms in northern Indiana, have some of the lowest rates of allergies and asthma in the westernized world, perhaps because of the so-called "farm effect," according to an international study.
Their allergy rates are about half that of their Swiss relatives, who have some of the lowest in the world.
Lead author and Indiana allergist Dr. Mark Holbreich said scientists believe the reasons are environmental and not genetic, even though the Amish are descendants of Swiss immigrants to the United States.
"They live on farms like the 1850s with no electricity and no TV and the children run around in the barns," said Holbreich. "A lot of their work and early life exposure is to things on the farm."
"This [study] would suggest that if you have early life exposure [to allergens], then somehow it drives the immune system away from developing allergies," he said.
"Large animals are part of it, and the straw bedding animals sleep on," said Holbreich. "And what [the Amish children] eat and the fact that their mothers are in the barn when they are pregnant."
The study, which was published in the April 16 issue of the Journal of Allergy and Clinical Immunology, was a collaborative effort with German researchers, who had previously looked at low allergy rates among Swiss farmers who lived in barns connected to their houses.
They studied 157 Amish families, 3,000 Swiss farming families and another 11,000 Swiss who did not live on farms. All had children aged 6 to 12.
Only about 10 percent of all Amish children show sensitization for allergies - mostly dust mites and grass; about 25 percent of all Swiss farm children tested positive to allergies - mostly cats.
Overall, the Swiss have the same allergy sensitization rates as Americans - about 44 to 50 percent. Only about 20 percent of those who show sensitization develop allergy symptoms.
Researchers also found that only 5 percent of Amish kids had been diagnosed with asthma, compared with 6.8 percent of Swiss farm kids and 11.2 percent of the other Swiss children.
Allergy rates are increasing in the United States and scientists have a variety of theories, including childhood obesity, diet and even immunizations.
One of the most important observations in the study was the benefit derived from drinking raw, unpasteurized milk.
Surprisingly, the dairy cows themselves are not raised any differently from the mainstream dairy industry, according to Holbreich.
"The Amish are not organic farmers," he said. "These are the same cows and the milk they sell goes to bottling - but something in the processing of milk changes."
Homogenization of milk breaks about its fat globules, Holbreich noted. "Maybe something about the fat globules is protective."
"The take-away point is not that we should become Amish," he said. "We aren't going to become Amish to prevent allergies."
But now, scientists can push their research forward to the next phase.
"Instead of just testing skin, we can look at a sophisticated measure of genetics and environment - the microbiome - the bacteria in the environment, the parasites - all the things you come into contact with."