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Study examines why kids growing up on farms are less likely to get asthma

Exposure to dirty farm air may help protect children from getting asthma later in life, according to a new study by researchers in Belgium.

Scientists have known for years that children who grew up on dairy farms are far less likely to develop asthma than children who grow up in other settings. But the Belgian team, from Ghent University, now has seen evidence in mice for why that is the case.

It works this way: Bits of bacteria, from manure and feed, found in farm dust trigger a temporary inflammatory response in children’s lungs that later protects them from asthma. A molecule involved in that defense mechanism is sometimes disabled in people with asthma. The researchers theorize that treatments involving the molecule early in life could be possible to avoid asthma.

Thomas Scott, MD, an allergy and asthma specialist with Ascension Medical Group, says the study is the latest to support the “hygiene hypothesis” – the idea that over-cleaning and the use of antibiotics has wiped out microorganisms that once taught a child’s immune system not to overreact to foreign substances. It’s one theory for why the number of Americans with asthma grew by 28 percent from 2001 to 2011, according to the Centers for Disease Control and Prevention.

“This study is interesting because most writing about the hygiene hypothesis revolves around allergies, and this one looked at asthma,” Dr. Scott says. “It’s a small leap, and not a surprising one, since most kids with asthma have allergies. They run together.”

He says the study also is of note because the cells involved are cells that line the airway – not just immune cells, which tend to be the focus on studies related to the hygiene hypothesis.

“This finding is consistent with evolving concepts about allergy and asthma,” Dr. Scott says, “that multiple systems interplay to lead to disease.”

Other studies have drawn similar conclusions regarding allergies and the exposure to pets and farm animals. The problem, Dr. Scott says, is no one has been able to find a way to use the findings to develop a protocol to help children, such as a treatment to expose children and prevent allergies or asthma.

“In fact,” he says, “some exposures can trigger a nasty asthma attack.”

So until more research is done, Dr. Scott doesn’t recommend parents take small children out to the farm just to try to protect them from allergies or asthma down the road.

“People shouldn’t allow their kids to get exposed for asthma prevention,” he says. “They may end up far worse than they bargained for.”