It was common practice to eat chewing gum off the footpath when I was young (eighties).... disgusting I know but it never made me sick. We ate crab apples and strange berries from bushes; any animal we saw was fair game for petting (be it a stray dog or a white mouse). I reckon I didn't wash my hands for days at a time when I was young and there would have been only one bath a week on a Saturday night. Most primary school years I got a Cert at the end of saying I had missed no days and I didn't take an antibiotic until I was 21 (and only then because I was in an accident, and none since). How times have changed! My nieces and nephews seem to have all sorts of ailments (eczema, asthma, etc.) I have no scientific proof of this but I think there is a lot to be said for not obsessing about hygiene.