Can milk intolerence come back?

Patient: My 2 year old son was diagnosed with a milk protein intolerence as an infant. We reintroduced milk at 18 months. He seemed to be fine for a few months but now he has chronic constipation, abdominal pain, weight loss, irritability, bouts of tiredness. Could this be the milk intolerence making a re-appearance? We are waiting on an appointment to see a pediatrician but wondered if we should eliminate milk in the meantime.

Doctor: