Farm dust helps children raised on dairy farms have reduced allergies and asthma, study says

A study published Thursday in Science says that "growing up on a dairy farm protects children from allergy, hay fever and asthma." Using mice as subjects, researchers said "that chronic exposure to low-dose endotoxin or farm dust protects mice from developing house dust mite induced asthma." Researchers said children growing up on dairy farms "breathe air containing bacterial components, which reduce the overall reactivity of the immune system."

The research is related to the hygiene hypothesis, "where a lack of exposure to microbes as a tyke leads to more allergy and asthma," Rachel Feltman reports for The Washington Post. "There's increasing evidence that farms have the best germs for preventing respiratory problems and allergic reactions later in life. One study found that just 25 percent of children living on Swiss farms reacted to common allergens like dust mites, pollen, animals and mold, while 45 percent of children in the general population reacted." Among Amish children, the rate is 8 percent.

"Scientists believe that the bacteria native to farms, especially ones that house livestock, may trigger something in children who live nearby," Feltman writes. "Scientists induced dust mite allergies in mice, then showed that exposure to dust from a dairy farm made early in life made them immune. Then, they studied the mechanism that was protecting the mice, making their mucous membranes less likely to react to the allergens. They found a protein called A20, which the mice were producing when exposed to the farm dust. When the researchers knocked out the A20 in their subjects' lungs, the farm dust stopped protecting them from allergic reactions." (Read more)