Breastfeeding provides optimal nutrition for babies and can also help prevent certain infections in babies. The World Health Organization (WHO) recommends exclusive breastfeeding for the first six months of a baby’s life.

Normally babies will not develop allergic symptoms while being exclusively breastfed. However, very sensitive babies can have immunological reactions.
This is not allergy to breast milk itself. It is an allergic reaction to small amounts of dietary proteins (e.g. cow’s milk protein, egg protein, etc) that are passing from mother to baby in the breast milk.

When allergic symptoms arise despite exclusive breastfeeding, the ideal solution is to eliminate these symptoms but maintain breastfeeding. This may be achieved by eliminating common allergens (e.g. milk, egg, wheat, etc) from the mother’s diet.
Such diets are complicated however and should not be attempted without the assistance of a doctor or dietitian: over-restrictive diets may be harmful to the mother’s health and can reduce the quality of her breast milk.
If a maternal elimination diet proves too difficult or ineffective, cessation of breastfeeding may need to be considered. This is a sensitive matter, which needs to be discussed between the mother and her doctor.