If your child continues to experience nausea, you may consider giving them over-the-counter medication like Gravol in various forms. It's also recommended to offer light foods like soups, toast with butter, or eggs, while avoiding heavy or sugary foods. Make sure your child stays hydrated and continues to eat small amounts even if they have a reduced appetite. Gastroenteritis usually lasts 48 to 72 hours, but if vomiting persists for longer than a week or if your child is unable to eat at all, it may be wise to seek medical advice.