It is important to ensure that your child is receiving a balanced and varied diet to support their immune system. In addition to a healthy diet, a multivitamin supplement may be beneficial if their diet is lacking in certain nutrients. You may also consider rinsing your child's sinuses during colds to help alleviate symptoms and prevent complications. It is recommended to use a syringe (without a needle) and saline or distilled water for this purpose. Following the proper technique and using the right amount of water for your child's age is crucial for best results.