When your child throws up, it is often caused by a virus. Your child may also have watery bowel movements (diarrhea). Most of the time, vomiting stops in 6 to 24 hours. The diarrhea may keep going for a day or 2 more. If your child has vomiting without diarrhea, and it lasts more than 24 hours, your child may have something more serious and needs to be seen.