Too sanitary

I was listening to Public Radio and heard Zorba Paster: On Your Health mention a study in which the health of lab rats kept in sterile conditions and that of sewer rats was compared. It was found that the sewer rats did not respond to whatever they were exposed to, because they had already built up an immunity to it. On the other hand, the rats from sterile conditions got sick. Also, when there was nothing attacking their bodies, their immune system started attacking the body itself (think asthma and allergies).

So, the suggestion is that we don't need to be 100% protected from everything, and that it might be better to be allowed to develop some natural defenses in childhood.

The next step of the study will be to create a fake sewer in order to be able to observe the rats throughout the life cycle to see how many survive childhood.

Here's a link to an article on it.