Nutritional, growth, and microbiome implications of oral immunotherapy: Unintended consequences and clinical considerations

Food allergy management has changed significantly, with oral immunotherapy (OIT) emerging as a widely adopted strategy to increase reaction thresholds and reduce the risk of severe allergic reactions. Alongside its immunologic effects, OIT has important implications for nutrition, growth, and the gut microbiome. Traditional management of food allergy relies on strict allergen avoidance, which may compromise dietary adequacy and growth, particularly in children who are avoiding nutrient-dense foods such as cow's milk and eggs. OIT offers an opportunity to reintroduce these foods in controlled amounts, potentially improving nutrient intake and supporting growth trajectories. Emerging evidence highlights the role of the gut microbiome in modulating immune tolerance. Microbial diversity, metabolite production, and early life colonization patterns influence regulatory immune pathways and epithelial barrier integrity. During OIT, microbiome changes seem modest and variable, with some studies suggesting taxon-specific or functional shifts rather than global restructuring. More importantly, dietary factors, particularly the use of ultraprocessed foods as dosing vehicles, may confound microbiome outcomes and influence treatment responses. From a nutritional perspective, OIT presents both opportunities and risks. Whereas allergen reintroduction may improve protein and micronutrient intake, reliance on energy-dense masking foods may increase the risk of excessive calorie intake and suboptimal diet quality. Growth outcomes during OIT seem generally favorable, particularly in younger children and those with lower baseline growth. This article summarizes current evidence on OIT, focusing on its interactions with diet, growth, and the gut microbiome, and highlights the need for integrated, multidisciplinary approaches to optimize both clinical and nutritional outcomes.