For the first few years after I was certified as an IBCLC I worked in a
pediatric practice which did RAST skin testing for allergies.  I recall one
of the peds talking about a 7 month old breastfed baby who had a positive
reaction to peanut butter altho he'd never had so much as a taste of it by
mouth.  He'd apparantly been sensitized (in utero? by breastfeeding?)  I
don't recall whether there was discusssion of how he was affected by mother's
consumption, but I suspect there must have been problems or why do the
testing?

I don't bother with lists of forbidden foods, but every so often I get a
dramatic situation where baby's reaction to antigenic protein coming through
HM is striking.  I had a mother with sore nipples which didn't respond to
anything (all the standard stuff.)  With nothing else left to try we decided
to eliminate foods known to be problems in mom's family.  We started with
dairy.  Nipples got better, tho pediatrician scoffed.  Any time mom came off
dairy elim -- even trace amts in food, nipples got tender.  At 4 mo. pp. baby
was in dad's lap while dad was eating ice cream.  Baby grabbed spoon and got
a taste as well as a few drops splashed on face.  Within 2 hrs baby was in
emerg. room with systemic reaction as well as scalded patches on face where
ice cream touched skin.
Barbara Wilson-Clay, BSE, IBCLC Austin, Tx