Human Milk Oligosaccharides (HMOs) represent a family of approximately 200 complex carbohydrates present in human milk. They are the third largest solid component in breast milk after fat and lactose. HMOs have been shown to strengthen the gut barrier function and to block pathogens. They are also known for their prebiotic effect and for promoting beneficial intestinal microbiota growth and stimulating the immune system. Currently there is scientific evidence linking HMOs and more particularly 2 FL and LNnT with the prevention of allergic sensitization. The results both from preclinical and clinical observational data, from the LIFE Child Cohort, demonstrates a positive effect of 2FL and LNnT in reduction of allergic sensitization.