My daughter is not lactose intolerant

I am going to use my bully pulpit to educate a bit now.

If a baby has an allergy or sensitivity to dairy if is almost never due to lactose intolerance. Lactose is a sugar found in milk. All milk. That includes breast milk. Lactose intolerant people lack an enzyme necessary to breakdown lactose. It is possible for a baby to be lactose intolerant, but this is extremely rare. This would amount to the baby being unable to digest all milk including breast milk. 100 years ago these babies would have died. No amount of cow milk that is removed from a mother's diet would resolve the intolerance. The only option for the very few babies this effects would be elemental formula.

When milk is an issue for an infant it is almost always due to an allergy or intolerance to milk protein. There are over 20 different proteins in milk. Lactoglobulin has been accepted as the major allergen in cow's milk protein intolerance, but any milk protein can potentially cause a reaction to someone allergic to dairy. A milk allergy occurs when the immune system mistakenly sees the milk protein as something the body should fight off. Intolerance is similar, only there is typically an irritation involved not a full blown immune response.

So, when your Great Aunt Milly says the allergy must have come from her side because she has a hard time digesting cheese you can smile and nod, but know, yourself, that the two issues are totally separate.