The Relationship Between the Environment and Our Immune System

People who live in cities, particularly ones with high traffic and therefore high pollution burden often have worse allergy problems than people who live in the countryside. There's a lot of different hypotheses as to why that happens. But one idea is the way that our immune system gets trained - whether we have a really kind of nice, diverse surroundings or not. The microbes that live inside us and on us and around us seem to be really important in how our immune system develops.