From Phillip Petersen:

Re: Being too clean may lead to allergies, study suggests (Nov. 29): This, to me, is a persistent fallacy that could only be held by a relatively young person (or an old one with a shoret memory) and no knowledge of domestic history. Our parents, grandparents and great-grandparents were, unless forced by extreme poverty, not less hygienic. In fact, they tended to scrub the hell out of everything that couldn't be boiled. The problem is surely not that we do more cleaning but what we use to do the cleaning.