SOME children avoid developing asthma because they live with cats. Now a team
of immunologists has found out why, and it’s not the answer many researchers
expected.
The finding that cats can protect children against asthma was originally
thought to support the “hygiene” or “cleanliness” hypothesis. According to this,
a lack of early exposure to bacteria or allergens keeps one branch of our immune
system, mediated by “Th1” cells, from developing properly. As a result, the
immune system gets out of balance and the other branch, mediated by “Th2” cells,
overreacts, causing the runny nose, sneezing and wheezing of allergic…
