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. The clinical manifestations of anemia are related to its etiology, severity, urgency and other factors. In acute anemia, such as acute blood loss or hemolysis, although the degree of anemia is mild, it can also cause serious symptoms or even shock; in chronic anemia, if the compensatory function of the organs is good, it can be asymptomatic or less symptomatic, and only when the compensatory function is incomplete do symptoms gradually appear. The main function of red blood cells is to carry oxygen, so when anemia occurs, the tissues and organs are deprived of oxygen and a series of symptoms are produced. 1. General manifestations: pale skin and mucous membranes are the prominent manifestations. In case of anemia, the skin (face, ears, palms, etc.), mucous membranes (lid conjunctiva, oral mucosa) and nail bed are pale; in case of severe anemia, the skin is often waxy yellow, which can be easily misdiagnosed as mild jaundice; on the contrary, jaundice, cyanosis or other skin pigmentation changes can conceal the manifestation of anemia. In addition, children with longer disease duration often have symptoms such as easy fatigue, dry hair, low nutrition, and delayed physical development. 2. Hematopoietic organ reactions: The bone marrow in infancy is almost exclusively red marrow. In anemia, the bone marrow cannot compensate further and extra-marrow hematopoiesis occurs, manifested by enlarged liver, spleen and lymph nodes, and nucleated red blood cells and naive granulocytes may appear in peripheral blood. 3. Systemic symptoms: (1) Circulatory and respiratory system: In anemia, accelerated respiration, accelerated heart rate, increased pulse rate, increased arterial pressure, and sometimes capillary pulsation can be seen. In case of severe anemia, heart enlargement, systolic murmur in the precordial area, and even congestive heart failure may occur. (2) Digestive system: Gastrointestinal motility and digestive enzyme secretion are affected, and loss of appetite, nausea, abdominal distension or constipation occur. Occasionally, tongue inflammation and tongue papillae atrophy may occur. (3) Neurological system: It often shows mental inactivity, inattention and emotional agitation. Older children may have headache, dizziness, black spots in front of the eyes or tinnitus, etc.