The type of germs that kids share with each other are different to what you can pick up from the dirt. I suspect (though I would love to find evidence) that upp

The type of germs that kids share with each other are different to what you can pick up from the dirt. I suspect (though I would love to find evidence) that upper respiratory infections are far more common today than they were in the past. We now have dense cities, global travel, compulsory schooling, and a large global population for colds and flus to diversify in. On the other hand we have less exposure to the bacteria and parasites that live in the dirt and on animals. They trigger (and modulate) a different part of the immune system associated with allergies.