dear user to treat the cause of that you should know these symptoms of vomiting with diarrhea and refers to viral or bacterial infection of your intestine..........infection of the intestine has many causes according to history of begining of symptoms the cause almost detected......... the most important test in this case is stool culture test .....you can give him ciplox 500 to treat bacterial infection if present stool culture is very helpfyl to detect type of infection as you may get infected with amoeba or salmonnela typhi or shigella or compylobacter bacteria or that should be managed with antibacterial drugs to get out your worry...........the first aim of investigations is to know the causative organism as the most common cause of these symptoms is salmonella that cause typhoid disease....he shouldnot get worry or stressed of these symptoms as stress will impair your immunity and cause symptoms to get worse....he should administer plenty of fluids and rice soup and tea with little suger that helps improvement and do stool culture to detect cause and treatment begin simply......dont forget that anxiety and stress can cause these symptoms as it affect smooth muscle of intestine ......i hope that helped you....wish you healthy life