The answer is yes. This happens by two main mechanisms. The first is lactose intolerance, or the inability to properly break down the sugar in milk called lactose. This can be diagnosed by testing, however, the easiest way is to allow your kid to have no diary for a few days, then give several ounces of a brand of milk called “Lactaid” (or similar). This milk has no lactose. If your kid tolerates this with no symptoms, then you have made the diagnosis. And if that is the case, avoiding dairy that has lactose is an appropriate way to proceed, or you may have your child take a tablet called “Lactaid,” which is the enzyme responsible for breaking down lactose. I personally take this when I am eating ice cream or other dairy.
The other way milk can cause diarrhea is by an intolerance (some would even say an “allergy”) to the protein in milk. This can be diagnosed the same as above with lactose intolerance, but the patient will get diarrhea with the Lactaid milk. The treatment is avoidance.
Hope this helps,
Albert G. Karam, MD