Infants or young children are more likely to have food allergies, because of their immature immune systems, will be allergic for harmful substances in food, another possibility is that infants bowel system is not fully developed, resulting in failure for casein digestion, resulting the chance of milk vomiting will be higher. The baby body's immune system can react to casein as allergens, causing the body to have allergic reactions. A survey show that there are around 2-7% of infants and young children, turned out to be sensitive to milk and other common food allergens, including egg white, seafood such as crabs, soy and peanuts.

Medical reasons for infant food allergy are inconclusive; believe is related to genetic, dietary habits and sensitive record to certain disease. If both parents suffer from food allergies, the child have a higher chance of suffering from food allergies, which the father or mother if there are food allergies, have the opportunity to be transmitted to children. The partial eclipse have the opportunity to indirectly cause food allergies, for example, most patients do not eat from small to a certain type of food, when a day to eat this food, the body have the chance to have allergic reactions. Another study also refers to the long-term emphasis on eating the same food, the body will consume specific digestion, trigger sensitivity.