PURPOSE OF REVIEW: We review the evidence that environmental stimuli that perturb naturally selected host-microbe interactions are driving the increasing prevalence of food allergy and examine the mechanisms by which commensal bacteria regulate tolerance to dietary allergens. RECENT FINDINGS: Antibiotic use and the consumption of a high-fat/low-fiber diet have a major and rapid impact on gut bacterial populations, with long-term consequences for both overall microbial community structure and the regulation of host immunity. Recent work emphasizes the role of mucosa-associated commensal bacteria in eliciting a barrier-protective response critical to preventing allergic sensitization to food. Murine model studies are informing the development of novel live biotherapeutic approaches as an adjunctive therapy to enhance antigen-specific oral desensitization and to promote lasting tolerance in patients with food allergy. SUMMARY: Strategies based on modulating the composition and/or functionality of the gut microbiome hold promise for the treatment of food allergy.