Annette:  My understanding is that babies are not allergic to breast milk
but can be allergic to proteins that get into the breast milk.  If the
baby is allergic to whey, casein, and lactoglobulin, these are probably
the cow's milk proteins he was exposed to in the formula.  Human milk
contains alpha-lactoglobulin, bovine milk beta-lactoglobulin (I hope I
got those the right way around).  There have been a few studies which
have shown benefit to allergic babies with exclusive breastfeeding when
the mother restricted her own intake of allergenic foods (in this case,
the mother would have to stop all cow's milk products, since the baby has
already been sensitized by the formula).  Some references you might find
helpful include: Chandra RK, et al. Influence of maternal diet during
lactation and use of formula feeds on development of atopic eczema in
high risk infants. BMJ 1989;299:228-30; Lucas A, et al. Early diet of
preterm infants and development of allergic or atopic disease: randomised
prospective study. BMJ 1990;300:837-40; and Host A, et al. A prospective
study of cow's milk allergy in exclusively breast-fed infants. Acta
Paediatr Scand 1988;77:663-70.  The hydrolysate formula works, but as you
said, it is so very expensive and doesn't provide the many other benefits
of breastfeeding.  So you're very justified to encourage this mother to
breastfeed.  Good luck! Alicia. [log in to unmask]