To check if an infant is allergic to milk protein, you need to do the following: 1. You can do a skin prick test on children. You can prick the reagent and place it on the infant’s forearm, and if the infant is allergic to a common object, it will have a positive result. If there is a milk protein allergy, there will be obvious redness and swelling at the site where the milk protein is dripped. 2. Allergen testing can be done for infants. Allergen testing is a blood test, which mainly detects the specific IgE concentration in the infant’s blood. If the milk-specific IgE concentration is significantly high, it suggests that the infant is allergic to milk protein. For milk protein allergy, the infant needs to be replaced with partially hydrolyzed or deeply hydrolyzed protein formula.