Cod liver oil is a fat extracted from the liver of shark, cod, etc. The main components are vitamin A and vitamin D. It is commonly used to prevent and treat vitamin A and vitamin D deficiency. Vitamin A and vitamin D are fat-soluble vitamins and are important bioregulatory factors in the body, both affecting the function of the respiratory system and digestive tract by participating in the body’s immune regulation. Usually used in the following cases: 1, breast-fed, mixed-fed or artificially fed children to prevent vitamin AD deficiency caused by rickets, night blindness and pediatric hand and foot convulsions. In addition, there is a large amount of literature proving the effectiveness of vitamin A and vitamin D supplementation in the treatment and prevention of diseases related to respiratory, digestive and immune systems. Therefore, it is necessary to regularly monitor vitamin A and vitamin D levels in children and supplement them in appropriate amounts to prevent respiratory and digestive tract infections, dry eyes, corneal softening and dry skin-related diseases. When cod liver oil is used for maternal use, it can also reduce the occurrence of colds during pregnancy, promote fetal bone and brain development, and make the baby born strong and healthy.　　2, one of the active ingredients of cod liver oil, vitamin A, can promote the growth of skin mucosa, maintain the normal operation of the nose, throat, lungs and other superficial layers, so patients with allergic rhinitis can use cod liver oil nasal drops to improve the resistance of the nasal mucosa, enhance the physical fitness of rhinitis patients, reduce the onset of rhinitis and reduce the symptoms of rhinitis.