To some extent, you seem to be trying to address the wrong problem. Although it is good that you are keeping your son hydrated, the dehydration is only a secondary symptom. The vomiting itself is merely the first symptom of some other problem, and is meanwhile the cause of the dehydration. What you need to do is find out why your son keeps vomiting. It is best that you visit a doctor for a diagnosis, as there are several disease and medical conditions that can cause chronic vomiting, and while some of these are relatively minor, others are extremely serious. Sometimes, a person who is vomiting continuously may require emergency hospitalization. In addition, repeatedly throwing up may cause other problems besides the obvious loss of fluids — for example, damage to the esophagus. If this happens, you may notice blood in your son's vomit.
There are a large number possibilities, so it is difficult to guess the cause without a thorough investigation of your son's condition, including the presence of any other symptoms. This may be a case of food poisoning, a particularly severe allergy, a bowel obstruction, or an eating disorder. Other possible causes include conditions such as a brain hemorrhage or tumor.
answered by G R