Can babies be allergic to their mothers or vice versa?

If you are referring to mother's milk, most babies are not
allergic to it. However, sometimes the diet of the mother, may include some proteins
that could affect the milk and may cause digestive upset in the baby. In terms of a
mother being allergic to a baby, there is a situation involving the Rh factor differing
in the mother and baby causing an immune response, almost like an allergic reaction. For
example, if a child has Rh positive blood(inherited from its father) and if the mother
is Rh negative, although their blood doesn't mix, after the birth of the first baby,
some of the Rh positive antigens enter the mother's bloodstream and she becomes
sensitized. She begins to produce anti-Rh antibodies. By the next pregnancy, if her next
child is Rh positive, these antibodies can cross the placenta and can attack the baby's
red blood cells. This can produce anemia (the blood has a low number of red blood
cells). This condition is called hemolytic disease  and can cause  brain damage,
illness, or death in the child. Fortunately, in this situation,an injection of Rh
immunoglobulin can be given to a mother before she becomes sensitized preventing this
reaction from occurring.