There are many different ways changes in human behavior can limit microbial exposure. Starting at birth, C-sections limit the microbial exposure provided by the vaginal canal. As we grow up and into adult life, spending very little time outdoors, a limiting diet, and not spending time around people could all limit our microbial exposure. An example of this would be someone who is homeschooled. So many pathogens thrive in classrooms which we jokingly refer to as “petri dishes” but they are important in the development of the immune system. There is a fine line between developing immunity and too much microbe exposure, but it is important, especially in early life, to develop tolerance and immune memory.
