HI, thanks for using health care magic Gastroenteritis is common in children, it is most commonly caused by a virus but can also occur as a result of bacterial infection. The most important part of treatment is maintaining his hydration because children are at risk of dehydration. This would mean replacing the fluid he is losing from vomiting and diarrhoea. Because of the vomiting he would not be able to take alot each time. If he is given too much , it would cause him to vomit. He should given 5mls (1 tsp) every 1 to 2 minutes, if this is tolerated the amount would be increased slowly. He needs 10mls per each kg to replace each diarrhoeal stool and 2 ml per kg to replace each episode of vomitus. For example if he weighs 10 kg and has stooled 5 times and vomited twice then he needs 250mls to replace for the diarrhoea and 40 mls for the vomiting. In addition he would need other fluids to maintain normal hydration. Your doctor would advise you on how much he needs exactly. I hope this helps