Over the years I have collected a lot of curious hypotheses how allergy develops. Only recently I ended this list as it became rather long – and to be polite – rather useless. Sorry, less polite – but nonsense at its best what this 62-year-old grandmother from Milano writes in Trends in Immunology in praise of a rough-and-tumble life. In line with the feebleminded “eat dirt” movement she writes
In this regard it might also be worth considering the contribution of the changes to children’s fashion over the past decades – namely that it has become customary to dress children with clothes covering their knees and elbows in their 1st years of life, leading to an important difference between the youth of earlier generations and that of more recent generations […]. Most of my generation stepped practically without discontinuity, from suckling mother’s milk to playing out side in the yard, and therefore the immune system was stimulated at an early stage by everyday abrasions to the knees, elbows and other extremities. Such abrasions would allow access of environmental antigens to dermal dendritic cells and prime a more Th1-like response.
Epithelial integrity may be important with respect to allergen exposure, but if you are in favor of bizarre allergy hypotheses you’d better go for the “cleaning agent”-hypothesis or the “prolonged diaper”-hypothesis, yea, yea.