Bifidobacterium longum is a probiotic bacterium that has been studied for its potential role in managing food allergies, particularly in children. Scientific validation exists but is limited and primarily based on preclinical and small clinical studies. The rationale stems from the observation that individuals with food allergies often have an altered gut microbiota composition, including reduced levels of Bifidobacterium species. B. longum is thought to modulate immune responses by enhancing regulatory T cell activity, promoting gut barrier integrity, and reducing inflammatory cytokines associated with allergic reactions.

Several animal studies have demonstrated that administration of B. longum can reduce allergic sensitization and severity of allergic reactions. Early human trials, especially in infants and children with cow's milk allergy, have shown that supplementation with B. longum (sometimes in combination with other probiotics) may reduce allergic symptoms and improve tolerance. However, results are inconsistent and the sample sizes are small.

Major clinical guidelines do not currently recommend B. longum as a sole therapy for food allergies, citing insufficient evidence. Most experts agree that while promising, more large-scale, well-controlled human studies are needed to establish efficacy and optimal dosing. Thus, the use of B. longum for food allergies is based on emerging scientific investigation, but routine clinical use is not yet supported by robust evidence.