PBMCs from children with cow’s milk or hen’s egg allergy, and healthy controls were incubated with α-GalCer, cow’s milk–sphingomyelin, or hen’s egg–ceramide. iNKTs were quantified, and their cytokine production and proliferation were assessed. Human CD1d tetramers loaded with milk-sphingomyelin or egg-ceramide were used to determine food-sphingolipid binding to the iNKT-T cell receptor (TCR). Here, CD1D is linked to allergic disease.