If your child is vomiting everything he eats and has diarrhea, it is important to monitor his hydration levels closely. You can try giving him small amounts of fluids like water or juice frequently to prevent dehydration. If your child refuses to drink or eat for more than 24 hours, or shows signs of dehydration such as very little or no urine output, no tears when crying, or being unusually tired, it is important to seek medical attention promptly. Dehydration can be dangerous, especially in young children, so it is important to address it promptly.