I spent my childhood camping! Weekends were spent catching snails, damming streams (which we later found a sheeps skull in, just upstream of those lovely dams), playing in mud, sleeping with just a few layers of cloth to seperate you from the ground/sheep sh*t. I am sure it helped my immune system. You need to encounter germs to be able to fight them. And If you are unprotected and suddenly get in contact with something ''unclean'' you may get seriously ill. So go out and get dirty! There's nothing like a good bit of mud. ;D