My one year old daughter, M, toddles toward a litter of kittens, who are fresh from a party in the litter-box and shakes her little butt as if to pounce.
“No!” my mother exclaims and reaches down to grab M.
“Let her play with them,” I say and grab her hand.
“What if she gets scratched?” She pauses. “Or worse. They might have dirty paws.”
“She’ll learn not to surprise creatures with claws, won’t she?”

Mom sighs and shakes her head. Is she right? Am I taking unnecessary risks? Of course I want to protect my daughter from any pain or discomfort. But is it possible to keep her too safe? The hygiene hypothesis is a theory that explains the increase in allergenic diseases such as asthma and allergies caused by a lack of exposure to microorganisms and infectious diseases in early childhood. The idea is that our immune systems need practice to effectively fight off illness, and children’s immune systems lose the ability to discern between an actual threat and an imagined one. As a result, they react strongly to things which should not be a concern, such as strawberries or peanuts. According to the FDA.gov even in the first few days after birth, an infant’s developing immune system needs challenges so that it can develop proper immunity throughout life. An expansion on this theory, called the Old Friends theory maintains that humans evolved alongside a host of microbial and parasitic organisms that are necessary for the human body to develop properly – without those germs, the body creates illnesses that might not otherwise have been there. This theory is being used to explain not only allergies, but more serious diseases such as diabetes, multiple sclerosis and digestive diseases such as IBD.

As it turns out, by keeping our homes sterile and grabbing the hand sanitizer every time they get a little dirt on them, we’re actually creating problems that might not have been there to start with. I know for my part, I’ll be letting M play with those kittens. Hopefully, her immune system will be the stronger for it.