I think this mother just does not want to breastfeed.  How can allergies
be passed on through the milk?  This makes no sense.  Allergies don't
come from antibodies, they come from antigens, and formula is full of
antigens.  Whatever antigens are in breastmilk are there in very small
quantities and come with factors (SIgA, macrophages) which help
"desensitize" the baby to these antigens.

No need for references; this is like asking for references to prove a
cow is not a horse.  If she doesn't want to believe, she doesn't want to
believe.  If she doesn't want to breastfeed, no references will convince
her.

Jack Newman, MD, FRCPC