Every three minutes, a food-related allergic reaction sends someone to the emergency room in the U.S. Currently, the only way to prevent a reaction is for people with food allergies to completely avoid the food to which they are allergic. Researchers are actively seeking new treatments to prevent or reverse food allergies in patients. Recent insights about the microbiome — the complex ecosystem of microorganisms that live in the gut and other body sites — have suggested that an altered gut microbiome may play a pivotal role in the development of food allergies. A new study, led by investigators from Brigham and Women’s Hospital and Boston Children’s Hospital, identifies the species of bacteria in the human infant gut that protect against food allergies, finding changes associated with the development of food allergies and an altered immune response. In preclinical studies in a mouse model of food allergy, the team found that giving an enriched oral formulation of five or six species of bacteria found in the human gut protected against food allergies and reversed established disease by reinforcing tolerance of food allergens. The team’s results are published in Nature Medicine.