Breast milk contains antibodies that can fight infection. Those antibodies are present in high amounts in colostrum, the first milk that comes out of the breasts after birth. However, there are antibodies in breastmilk the entire time a mother continues to nurse. Through these antibodies, the mother can pass on some protection from infectious illness she had in the past, and those she gets while breastfeeding. Breast milk can literally give babies a head start in preventing and fighting infections.