Fascinating research note in the journal Allergy. Called “Hypothesis: urbanization and the allergy epidemic — a reverse case of immunotherapy?”, it argues that migration from urban to rural areas increases the risk of allergy.
As the author says, it is almost a paradigm in allergology that allergen avoidance is beneficial. But that is where the trouble begins:
… it is hypothesized that the association between urbanization and increased risk of allergy may be explained by a decreased exposure to allergens such as pollens leading to lower tolerance to pollens. Through nonspecific effects on the immune system, this may also lead to lower tolerance to allergens in general increasing the susceptibility to allergic disease: a reverse case of immunotherapy! The rising trends of allergy may thus, in part, be explained by changes towards urban lifestyle including exposure to lower doses of allergen due to more time spent indoors and away from areas abundant in natural allergen sources.
Now there is an unintended consequence for you: By decreasing the prevalence of allergens in the environment we are doing ad hoc reverse immotherapy, neatly creating allergic responses where they did not exist before.