It has always puzzled scientists that children who grow up on dairy farms are much less likely than the average child to develop allergies and asthma. Now, they found a possible explanation: some bacteria found in farm dust could trigger an inflammatory response that later protects them from asthma. At least, that’s what they in a study on mice. This could mean that breathing in dust from dairy farms could protect kids from developing allergies or asthma. The theory supports the well known “hygiene hypothesis,” which is one of the explanations for asthma being the most common chronic disease in the developed world. The hypothesis suggests that children who grow up in households that are too sterile and clean don’t build a strong enough immune system.