Repeated vomiting: The child vomits nearly every time he or she tries to drink something. This type of vomiting makes it impossible to keep down any fluids or solid food, which greatly increases the chance of becoming dehydrated. The child has an even greater chance of dehydration if he or she also has diarrhea.

Occasional vomiting: Some young children vomit every once in a while for no clear reason. This usually does not increase the risk of dehydration or other problems as long as the child can keep down fluids between vomiting. The more time that passes between episodes of vomiting, the less serious it probably is. But if the vomiting continues, it may be important to find the cause.