It is possible that the red patches on your baby's cheeks and ears are a reaction to the milk he is drinking. It's important to monitor if the patches reappear after feedings and if they coincide with his milk intake. Since the patches disappear right after feeding, it may not be a major concern at the moment. However, if the symptoms persist after a few days, it might be wise to switch to a different type of milk or consult with a pediatrician to confirm a milk allergy. It's common for infants to develop milk allergies early on, but they may outgrow them by the age of 3. Keep an eye on any changes in your baby's condition and don't hesitate to seek further help if needed.