The prevalence of food allergy and other allergic diseases continues to rise within the industrialized world, yet the cause of this epidemic remains elusive. Environmental factors such as microbial exposures have more recently been implicated as one possible driving factor behind the increasing burden of allergic disease. The impact of gut microbiome on human development, nutritional needs, and disease has become evident with advances in our ability to study these complex communities of microorganisms, and there is a growing appreciation for the role of the microbiome in immune regulation. Several studies have examined associations between changes in the commensal microbiota and the development of asthma, allergic rhinitis, and asthma, but far less have evaluated the impact of the microbiome on the development of food allergy. In this article we review the human gastrointestinal microbiome, focusing on the theory and evidence for its role in the development of IgE-mediated food allergy and other allergic diseases.