If infants often have recurrent respiratory tract infections or digestive tract infections, they can eat the following medicines or foods, which can effectively improve immunity. First, eat more high-quality protein, because after eating fish, shrimp, eggs and milk and other high-quality proteins, the content of high-quality proteins in these substances is relatively high, which can effectively promote growth and development, and help to increase the concentration of antibodies in the blood, thus improving immunity and reducing the frequency of illness. Second, the application of astragalus oral solution, because astragalus oral solution has obvious tonic qi, spleen, solid surface effect, can effectively stimulate the improvement of immunity, so as to reduce the symptoms of low immunity.