Allergies And The Hygiene Hypothesis

Bolstering the theory that modern society’s fixation on cleanliness might actually be hurting the development of healthy immune systems in children, a new study published this week in the journal Science suggests that exposure to the kinds of bacteria found in the farmyard may actually protect children from allergies, hay fever and asthma.

The development of asthma and allergies is complicated and involves many factors both environmental and genetic. Asthma and allergies, which are strongly linked to each other, are among the most common diseases in the industrialized world. But several studies have shown that in the last few decades there has been a surge in the number of people in developed countries who’ve developed asthma or allergies.

There are many theories offered to explain this surge, one, the “hygiene hypothesis,” suggests that an increasingly sanitized environment inhibits the development of the immune system, making people more prone to allergies and asthma.   Another theory is that increasing exposure to chemicals and pollutants are the culprits.

Allergies of a Feather Flock Together
People with allergies tend to be allergic to multiple things. Sometimes this makes sense – being allergic to cats and dogs for instance – other times the groupings make you scratch your head. Based on our research survey data, we found that if you are allergic to one insect’s sting, it is more likely that you’ll be allergic to another. But food allergies do not appear to be associated with other kinds of allergies.You can learn more about these associations here.

In the study published in Science researchers looked into why children who grew up on dairy farms appear to be protected from allergies, hay fever and asthma.

In mice, researchers found that low-dose exposure to farm dust triggered an inflammatory response that later protected the mice from developing asthma induced from dust mites. Looking at the biology, the researchers found that the exposure modified a particular enzyme, A20, which is involved in this defensive inflammatory mechanism.

For many with asthma, that enzyme is disabled.

While the new study adds more support for the hygiene hypothesis, the researchers said they still must look at to see if this protective mechanism lasts into adulthood.