Hello, it is important for this condition to keep your son well hydrated, to counter the effects of the fluid that he is losing. At this age, viruses such as rotavirus can cause watery diarrhea. It is best to avoid all milk products since they will be more difficult to digest when the gut is inflamed. Testing to include parasitic disease may also be indicated. Giardia is one infection to consider at the local hospital. Suggestions for keeping your son well hydrated, include providing clear liquids without any bubbles. Pedialyte is a balanced electrolyte formula that can be purchased. If you don t have this and can not purchase it, diluting Gatorade 1/2 and 1/2 with bottled water can provide some electrolytes as well. In addition, rice, toast, bananas and yogurt may help. Thank you for your question, and if you need further assistance, please fax your questions to US 858 259 9689, PRMG medical group, the group accepts electronic consultations that is billed to your insurance. No out of pocket expense will be charged to you.