Hello Doctor, my baby is 3years 9months old he eats well but he get sick very frequently and his immunity is also weak, so I want ask what food products I have to give him to boost his immunity

A. till 5 to 6 yr of age kids have low immunity. 9give immunity booster food substance like-Eggs, youghrt, oats, citrus fruits, spinach, nuts like almond, wallnut, sunflower seeds, apple, and all seasonal fruits and vegetables