Breastfeeding should be the FIRST choice if your child can take anything by mouth. Because of the ease and rapidity with which breastmilk is digested, even if your child vomits or stools shortly after nursing, he will still have retained some of the nutrients. Other foods that are often suggested (such as Pedialyte, sports drinks, gelatins and sodas) offer little nutritional value and none of the antibodies that human milk contains.
When your breastfed child is ill you'll want to offer more frequent feedings -- this can limit the volume taken in at one time and helps to comfort and soothe a sick child. If your child is vomiting often and not keeping the milk down for long, it may be helpful to breastfeed frequently but limit the length of each nursing session (so your child takes in less milk at once). Another option is for Mom to express some milk before breastfeeding so that the milk flow is slower. RARELY does the baby who is allowed to breastfeed at will during a vomiting or diarrhea illness become dehydrated.