likeaninja the 'from birth' bit puzzles me too. 7yo DS has had problems since he was a few months old, although he's not too badly affected. DD doesn't have any allergies though. I wonder if his EMCS freaked his poor little immune system out.
Again, I've always been outdoorsy and far from a hygiene freak
.
The dc's have always got mucky in the garden and I've never dusted in my life.