Hi and welcome to Healthcaremagic. Thank you for your query. I am Dr. Rommstein, I understand your concerns and I will try to help you as much as I can. If this lasts for so long then the first thing to rue out is parasitic infection. You need to do stool culture on most common parasites such as Ameba, pinworms or echinoccocus. However other causes may be considered as well such as inappropriate diet. If this is caused by diet then he should try to rest more and switch to a diet of clear liquids. Drink water, juice, bouillon and weak tea to avoid becoming dehydrated. Replace lost fluids and electrolytes with sports drinks. Avoid coffee or soft drinks that contain caffeine, since caffeine increases the loss of water and salt. If you have nausea in addition to diarrhea, take very small sips of fluid frequently and suck on ice chips. He also may consider over-the-counter medications such as bismuth subsalicylate (Pepto-Bismol) or loperamide (Imodium).In cases of infectious diarrheas, you should do microbiologist testing of stool and see the exact microbe and then antibiotics can be used additionaly. I hope I have answered you query. If you have any further questions you can contact us in every time. Kindly regards. Wish you a good health.