>Of course, it is theorised that the antiseptic, sterilised world that we're all encouraged to live in now leaves kids unchallenged by any harmful microbes and thus having never built up any immunities. I used to have my kids eat their meals off the kitchen floor a few times a week. :-)

When I was a teenager, I heard that my then doctor used to sterilise everything her kids used, specially forks and spoons. Then the kids would stay with their grandmother over a weekend, and she'd find them playing with the chickens, drinking the same water chickens did :).

And both kids are doctors now...

Since my wife is a doctor, and we knew this story (and several others) from the beginning, we weren't as strictly sterilising stuff. Their bottles were microwaved quite often, but then not as strictly - and our kids got to play with soil, on the floor... they had their sampling of the current assortment of germs along the way. And guess what - they never caught anything serious (knock on wood).