There is no specific risk associated with letting a 4-year-old eat a green apple, as apples are a healthy fruit option for children. However, there are some general precautions to keep in mind: 1. Allergic reactions: Apples are not common allergens, but it is essential to monitor for any allergic symptoms if the child has never tried apples or has known food allergies. 2. Choking hazard: For a 4-year-old, it's important to cut the apple into small, manageable pieces to minimize the risk of choking. Remove the skin if the child has difficulty chewing it, and always supervise them while eating. 3. Pesticide exposure: Apples can have pesticide residue on their skin. To reduce exposure, wash the apple thoroughly before eating and consider purchasing organic apples if available. 4. Dental health: Green apples are more acidic than red apples, and acidic foods might contribute to tooth enamel erosion over time. Encourage the child to rinse their mouth with water after eating the apple and maintain a regular dental hygiene routine. As long as these precautions are taken, there should be no significant risks associated with letting a 4-year-old eat a green apple.