If your 5-month-old baby is vomiting and has diarrhea, it is important to consult with a pharmacist who may prescribe a medication like Gravol to help with nausea and vomiting. It is also important to ensure your baby stays hydrated by encouraging them to drink fluids, such as milk or infant formula, in small amounts frequently. Make sure to seek medical advice if you have any concerns about your baby's health.