It seems every few years a new study comes out linking people who grew up on a farm with having fewer allergy problems. Anecdotally, it makes sense – how often do you see a farm kid with hay fever? I just wish my genes had gotten the memo. I'm one of the exceptions here, and this time of year, with all the ragweed pollen blowing around, it can be difficult to get outdoors without coming back inside with a runny nose and itchy eyes.
Here's how allergies work. They're essentially an overreaction triggered by the immune system in response to an otherwise harmless substance. Many studies have shown allergies are genetic. However, more recent research indicates there's another factor at play: modern society is too clean. That is, there's a lack of exposure to microbes, bacteria, or other infectious agents that help train immune systems to recognize allergens – what's become known as the hygiene hypothesis.
A new study published in the September issue of Science may explain one of the reasons why: kids growing up on farms, especially dairy farms "breathe air containing bacterial components, which reduce the overall reactivity of the immune system." The study, conducted by Ghent University in Belgium, involved exposing mice to bacterial endotoxin, or farm dust before they received an allergic stimulus. Sure enough, mice exposed to the bacterial endotoxin were protected and didn't develop an allergic response.
That's not to say, by any stretch, that modern medicine and sanitary living conditions are a bad thing. Studies have shown there is no evidence that reducing modern practices of cleanliness and hygiene would have any health benefit. The more practical proposal has been to get kids outdoors, and in many cases, exposed to agricultural environments.
According to the Center for Disease Control's most recent National Health Interview Survey, conducted in 2012, 7.5%, or 17.6 million adults in the U.S. were diagnosed with hay fever, or allergic rhinitis, in the last year, and 9.0% or 6.6 million U.S. children reported hay fever in the last year.
If you aren't one of them, and can sit in the combine or tractor all day without coming home and feeling congested, you can probably credit growing up on a farm.