What's wrong with this picture?
The first problem with Dwight's take on the hygiene hypothesis is that he is confusing immunity against infection with protection against allergies. The second is that by the time you're old enough to eat phlegm-drenched toast for breakfast, it's too late to confer ironclad immunity against infection or allergy, because you need to develop it in early childhood. (Perhaps, in his toilet-side collection of medical journals, Dwight confused the hygiene hypothesis with a recent study showing that infants and toddlers in daycare who get sick a lot tend not to get sick as often once they hit kindergarten and beyond. Details, Dwight. Details!).
The biggest problem, though, with this pop culture view of the hygiene hypothesis is that in two decades of research since Strachan first made his comments, things are turning out to be far more complicated than anyone imagined. In short, research is showing that exposure to some bugs and allergens at an early age can protect us from allergies, while others do the opposite, triggering your body's immune system to go haywire and exacerbate allergic symptoms. Why one trigger would protect while the other irritates our bodies probably has everything to do with how our immune system reacts and is regulated, though many details are still beyond our scientific grasp.