Iron deficiency anemia is a clinical anemia characterized by small-cell hypochromic anemia, reduced serum ferritin and effective iron therapy due to reduced hemoglobin synthesis caused by iron deficiency in the body. The disease has the highest incidence in infants and children, and is most common from 6 months to 2 years of age. It is a serious health hazard for children and is a common disease of childhood that we focus on preventing and treating. There is hemoglobin in each red blood cell, and iron is an important part of hemoglobin. So if there is iron deficiency, the amount of hemoglobin in each red blood cell will decrease and the total hemoglobin of red blood cells will be lower than normal. In iron deficiency anemia, the red blood cells are small in size (small cells) and low in hemoglobin content per red blood cell (low pigment), i.e. iron deficiency anemia is characterized by small cells and low pigment. 1. General manifestations: gradual pallor of skin mucosa, more obvious in lips, oral mucosa and nail bed, easy fatigue and inactivity. In older children, dizziness, blackness in front of the eyes, tinnitus, etc. 2. Extramedullary hematopoietic manifestations: due to extramedullary hematopoiesis, liver and spleen may be mildly enlarged; the younger the age and the longer the disease duration, the more severe the anemia and the more serious the enlarged liver and spleen. Non-hematopoietic symptoms: (1) Digestive system symptoms: loss of appetite, a few have heterophilia (e.g. mud, wall cinder, etc.); vomiting and diarrhea may occur; stomatitis, tongue inflammation or atrophy of tongue papillae may occur; atrophic gastritis or malabsorption syndrome may occur in severe cases. (2) Neurological symptoms: manifested as restlessness or depression, mental inattention, memory loss, and intelligence mostly lower than that of babies of the same age. (3) Cardiovascular system symptoms: the heart rate increases when the anemia is obvious, and in serious cases, the heart enlarges and even heart failure occurs. (4) Other: Infections are often combined with reduced cellular immune function. Anti-nails may appear due to abnormal epithelial tissue.