A balanced diet is the key to a healthy immune system. Make sure your kid’s diet includes plenty of fruits and vegetables that are rich in antioxidants like oranges, carrots, spinach, bell peppers, green beans, etc. It is also necessary to focus on their gut health for which a good intake of prebiotic and probiotic are a must. Yogurt, buttermilk, banana, oats, etc. are great for increasing good bacteria in the gut.