Four-year-old boy vomiting, but no fever, and good mental state may be indigestion, gastroenteritis and other causes, such as persistent unrelieved, it is recommended to go to the hospital for treatment, such as vomiting after the relief of the symptoms, can be temporarily observed. Vomiting without fever may be caused by indigestion, unclean food, cold, gastroenteritis, etc. The symptoms of infection may be mild; good mental state indicates that the vomiting symptoms are not serious, and there is no electrolyte balance disorder or dehydration for the time being, so if there is no discomfort after vomiting, it can be observed for the time being. If there is still abdominal discomfort after vomiting, or accompanied by other symptoms, such as dizziness, elevated body temperature, mental state deterioration and other symptoms, it is recommended to consult a doctor in a timely manner.