IL4 and Allergy: Interleukins are present in breast milk, although their concentration is highly variable between women.9 Breast milk from mothers with allergies is higher in IL4 concentration when compared to milk from mothers without allergies.10,11 IL4 is relevant to the preterm population because serum IL4 induces both antibody and IgE production,12 although it is unclear if exogenous milk IL4 has this effect on the breastfed infant.