I nursed both my boys, who are each milk allergic.  (Yet do NOT test positive
to milk allergies... another story!)  They have reflux as well, which
complicates things.  I had to stop nursing my first at seven months because he
simply could not tolerate my milk.  I had stopped all dairy products, eggs,
oranges, apples, and every other item he currently cannot eat, yet he still
could not tolerate my milk.  It was heartbreaking, yet necessary to put him on
a hypo-allergenic, predigested, non-dairy formula.  We had a new baby one week
later!

I am happy to say I am still nursing my youngest (over one year), who is
having no problem tolerating my milk.  I haven't had dairy in a LONG time, but
it is worth it, and I feel good!

FYI:

Although my son did not have Alactasia, I found the following quote
interesting:

Jane Zukin's book, "Dairy-Free Cookbook," (Prima Publishing, 1991, page 7)
states, "Alactasia is another name for congenital lactose intolerance. Since
lactose is present in mother's milk, being born without the ability to digest
it would be inconsistent with life itself. Yet it does happen. Infants who
have symptoms of alactasia need to be treated immediately because prolonged
diarrhea may cause failure to thrive or fatal dehydration."

Good luck to all!

Katherine Murray
http://users.aol.com/katherinez/kath2.htm
"Children with Milk, Egg and Other Food Allergies"