Usually when it is recommended that a breastfeeding mother eliminate dairy produce from her diet, it is because of a problem that may be caused by the protein it contains, not because of lactose intolerance. Human milk is full of lactose, and nature has made certain that babies and toddlers can digest it.

Symptoms of milk allergies in babies include:

Frequent spitting up.
Vomiting.
Signs of abdominal pain, or colic-like symptoms, such as excessive crying and irritability (especially after feedings)
Diarrhea.
Blood in stool.
Hives.
A scaly skin rash.
Coughing or wheezing.