"It is ironic that we feed the most allergenic food known
to man, to our babies and children. B-lactoglobulin, a substance
found in cow's milk, but not in human milk, is foreign to the
baby's digestive tract. Newborn babies have increased gastrointestinal
permeability to B-lactoglobulin, probably because of a lack of
enzymes to digest it. Casein is another of the most allergenic
proteins in milk.
Allergy to milk creates gastrointestinal bleeding, leading to
iron-deficiency anemia in infants due to a loss of blood in the
stool. If the blood comes from high up in the intestinal tract,
it will appear as dark or black and is not readily recognized.
This blood loss can go undetected for long periods resulting in
iron deficiency in the child. Other diseases that have been associated
with milk include celiac disease, chronic diarrhea, various gastroenteropathies,
pulmonary manifestations and fibrosis."
From the book Allergies, Disease in Disguise.