UC San Diego

It is now well accepted that our modern lifestyle has certain implications for our health (Schaub et al., ), mainly as a result of our willingness to remove ourselves from the biological diversity of our natural environments (Roduit et al., ), while still being drawn inextricably to interact with it (Kellert and Wilson, ). Much of our interaction with the biological world is shaped by our interaction with the microbiological world. The bacteria, fungi, viruses, archaea and protists that comprise the microbiome of this planet, are also key to the development and normal functioning of our bodies. Our immune system is built to shepherd our microbial exposure, ensuring that microbial organisms that we need are kept close (but not too close), and that less-desirable organisms are expelled or killed before they can do too much damage. By moving from a life interacting with nature on a regular basis, to a life in which we isolate ourselves physically from natural microbial exposure, we may have instigated one of the great plagues of the 21st century; chronic immune disorders.