My experience with this is similar to what others have shared.  Most recently
a mother of a 6 month old, who had recently introduced solids, & ABM (only a
total of 4-5 ounces over a month), whose baby started showing some blood in
the stool, and her Ped recommended no breastfeeding, putting baby on a
predigested ABM, and wanted to do some invasive diagnostic procedures,
including a colon biopsy just to rule out a rare disease (I can't recall
what).  Ped admitted it could be just irritation, or benign polyps, but said
it wouldn't help for mom to cut out dairy, etc.

The mother got a second opinion from my favorite PA, who was sure that the
recent intro of both solids and ABM to be the culprit, and recommended
removing those from baby's diet, and that mom go on a milk-free diet.  Mom
was a heavy on the dairy type person, but she did was successful in removing
all dairy, and wonder of wonders,  baby had 3 stool samples come back clear.
 Mother also noticed health benefits to her self on the dairy free diet,
which is typical of what I've seen in these kinds of cases   The PA felt that
the predigested ABM would not guarantee no reaction, and that since the
infant had not experienced symptoms prior to adding the solids & ABM, that
the  breastmilk would not overtax the infant's system, and of course the
risks involved in depriving infant of immunological properties of breastmilk,
and the emotional risks of sudden weaning were not acceptable.

My understanding is that it takes about 3 weeks for mom's body to clear all
cow's milk protein from her system after she's gone milk free, and I tell
mom's not to expect to see results prior to that, but some do see results
earlier.