"I get about 5,000 e-mails a year from patients all over the world asking what to do," he said. "People know that something isn't right. They keep their kids in the cleanest environments and they get asthma. We get all of these things that were rare becoming common. And a lot of it comes down to hygiene. Excessive hygiene can potentially lead to disease."
The "hygiene hypothesis," which was first proposed nearly two decades ago, argues that aspects of cleanliness prevent the immune system from programming itself to fight off disease.
"The big question is what are those aspects? We don't want to go back to the standards of the 1800s," Weinstock said. "Public hygiene and cleanliness are very good for us, but removing ourselves entirely from our natural environment is bad for us. We need to figure out the aspects of dirt and exposure that are good for us and hopefully we can find a balance."
This idea has been kicking around a lot lately. I find the basic idea intriguing but it will be devilishly difficult to demonstrate. After all, it's not like you can control kids' behavior through several years to the extent required by clinical trials. But it's interesting enough to pursue, I think.