India, Jan. 19 -- Food allergies have been increasing dramatically across the developed world for more than 30 years. For instance, as many as 8 per cent of children in the U.S. now experience potentially lethal immune system responses to foods like milk, tree nuts, fish and shellfish. But scientists have struggled to explain why that is.

A prevailing theory has been that food allergies arise because of an absence of natural pathogens such as parasites in the modern environment, which in turn makes the part of the immune system that evolved to deal with such natural threats hypersensitive to certain foods.

In a paper published January 14, 2021, in the journal Cell, four Yale immunobiologists propose an expanded explanation for the rise ...