Dr. Greene`s Answer:
One of the most common reasons for blood in a young baby’s stools is an allergy to the cow’s milk protein in dairy products. The same allergy that can cause inflammation in the intestines (colitis) can also cause eczema in the skin. The allergy is not to breast milk, but it is true that enough cow’s milk protein from mom’s diet can come through in the breast milk to cause symptoms in an allergic baby. (Other food allergies can also do this. Milk is the most common, but enough soy, peanut, and eggs can also go through breast milk to cause allergic reactions).
La Leche League is right that the offending foods are usually gone from the breast milk within seven days of removing them from mom’s diet — often even sooner. Most allergic babies do get better while breastfeeding if their mothers give up cow’s milk and foods that contain cow’s milk (which can show up as whey, casein, milk hydrolysates, butter on food labels). But, even after avoiding cow’s milk, there are a few babies who do not improve. If your baby doesn’t get better, you might try eliminating all four of the most common allergens from your diet (milk, soy, peanuts, and eggs). Be sure you find another way to get plenty of calcium.
I would not stop nursing for this unless, perhaps, if your baby were anemic and/or had low protein on a blood test. Even then, I would recommend seeing a pediatric GI doc before deciding to stop. There would probably be a safe way to continue nursing.
Many doctors are not aware of this, but even though Nutramigen is a great hypoallergenic formula that can be very effective for babies who are allergic to milk-based formulas, it does still contain traces of milk. In my experience, those who react to traces of milk in dairy-free breast milk will also react to Nutramigen (within a few weeks, if not at first) and would ultimately need a formula called Neocate, which contains none.
In short, I admire your decision and your pursuing more information. The advantages of nursing far outweigh a tiny bit of inflammation and blood loss in an otherwise growing baby. I wouldn’t stop nursing for that.