Similac Pro-Sensitive helps strengthen your baby?s immune system to be more like a breastfed baby than ever before. How? Similac with 2?FL helps support baby?s developing immune system by closing multiple gaps in immune function* between formula-fed and breast-fed infants. Unlike other formulas, Similac has 2?FL HMO, a prebiotic that circulates throughout the body. Our sensitive formula is designed for fussiness and gas due to lactose sensitivity. Similac?s biggest breakthrough in nearly a decade comes in two gentle formulas: Similac Pro-Advance and Pro-Sensitive. *As measured in blood samples in a clinical study