In 1976, a paediatrician named John Gerrard noticed a peculiar pattern of diseases among the people of Saskatoon, the Canadian city that he had called home for twenty years. The city’s white population was more likely to get allergic diseases like asthma, eczema, and hives than the indigenous Metis communities, while the latter were more often infected by tapeworms, bacteria, and viruses. Gerrard wondered if those trends were connected, if allergic disease “is the price paid by some members of the white community for their relative freedom from diseases due to viruses, bacteria and [worms]”.
