Growing up on a farm could provide lifetime protection from allergies and asthma.
Respiratory allergies are the most common form of allergy in American children; about 17 percent of kids in the US suffer from these types of allergies. And about 6.8 million American children currently have asthma. But studies show that these conditions aren’t distributed uniformly among all children. Children raised on farms — most notably dairy farms — have lower rates of allergies and asthma. That’s why researchers are looking into the farm environment itself; if they can figure out the mechanism that’s protecting children who grew up in rural areas, they might be able to engineer drugs that can help those that live in more urban environments, too.
The scientists found that mice who breathed in tiny particles of a protein commonly found in cowsheds developed stronger immune systems. Belgian, Dutch and French scientists found that regular exposure to bacteria particles and farm dust protects children from allergies because it blunts their inflammatory immune responses. The protective effect was due to a protein, A20, which is produced in the lungs after contact with farm dust and prevents inflammation. Inflammation of the airways leads to the difficulties asthmatics have in breathing.
One of the key protective elements found on farms is endotoxin. Endotoxin is a protein found in bacterial cell walls, and is also found in smaller quantities in household dust.
Dr. Martijn Schuijs of Ghent University said, “In children, allergic sensitization and asthma are strongly influenced by genes and the environment. A dairy farm is one of the strongest protective environments. On farms, there is high-level exposure to endotoxin, a cell wall component of Gram-negative bacteria. The protective effect that high levels of environmental endotoxin demonstrate against allergy has also been noticed in nonfarming households, where exposure was measured in dust collected from mattresses or kitchen floors. The hygiene hypothesis states that the rise in allergy and asthma that has been observed in affluent countries since the Second World War is caused by reduced “infectious pressure” from the Western lifestyle environment.”
The study, which was published in Science, involved exposing mice to endotoxin every other day for two weeks and then to particles taken from house dust mites – the most common cause of asthma in humans. Mice regularly exposed to endotoxin did not develop allergic features, while control mice did. Endotoxin exposure appears to have protected the mice by preventing the animals’ lung epithelial cells from generating molecules that caused inflammation of the lungs.
The researchers then turned to humans, using lung biopsy samples from healthy adults and asthmatics. After regular exposure to endotoxin, healthy human cells generated fewer inflammatory molecules characteristic of allergies than their asthmatic counterparts, in whom A20 levels were also lower.
This suggests that farming and other similar environments protect against allergy with this enzyme’s help.
In the meantime, the study shows that exposing children to farm environments early in life is probably a “good idea,” Lambrecht says. “In Holland and in Germany, there’s a lot of farms who are now organizing daycare centers,” he says. “It’s a crazy idea, but it’s happening as we speak in Western Europe; this study shows that we shouldn’t be afraid to do that — to send our kids to farms for daycare.”