My Grandson Is 5 And Has Had Intermittent Diarrhea For

My grandson is 5 and has had intermittent diarrhea for 4 weeks. It will stop for 3-4 days then return. The Dr has done feces testing and we have eliminated dairy. He can home again with diarrhea tiredness and fever. He does not always have fever just when it began and again now. The Dr wants to continue eliminating foods for now. What else could it be/