It’s a great theory - but one that I can’t agree with, at least, this can’t be the sole reason for the rise and rise of allergies in the West. I used to play in the fields next door to my house for all of my childhood years. I’d be climbing trees, falling out of them, messing about in mud, chasing other kids with sticks and generally playing about in a ‘dirty’ environment. As a child, I never got hayfever. As an adult, hayfever is killing me. My eyes go blood red, they itch like hell, my nose runs, I sneeze all the time, my throat itches. And I susspect my eyes get set off by cat hair too - which never happened when I had a pet cat as a kid.