1, repeated respiratory infections, pay attention to whether iron deficiency often cold, almost once a month, eat a lot of drugs to increase resistance, food, but the disease still reported on time, the mother is very anxious. For children with recurrent respiratory infections, it is important to test for iron deficiency. Iron deficiency not only leads to anemia, but also impairs the bactericidal ability of phagocytes, which in turn affects the body’s defense ability, leading to a decrease in the body’s ability to fight infection and susceptibility to infectious diseases. Iron deficiency can also adversely affect human behavior and intellectual development, often resulting in dullness, irritability, inattention, reduced learning ability and memory, and easy fatigue in severe cases. In addition, iron deficiency will affect the normal development and growth of the body, resulting in delayed growth and abnormal bone development. Calcium is one of the most important elements of the human body. Calcium deficiency affects the development of bones, but also leads to weakened digestive function, low immunity, high blood pressure, visual fatigue, etc. If calcium is not supplemented as needed, children may miss the best “sunrise” period for calcium supplementation. If calcium is not supplemented as needed, children may miss the best “sunrise” period for calcium supplementation. But now the trend of “universal calcium deficiency” may be a bit exaggerated. Zinc is mainly involved in the synthesis of enzymes in the human body. If you find that your child has the following symptoms, you should be highly alert for zinc deficiency and need to measure serum zinc: (1) anorexia, loss of taste, heterophagia. (2) Blurred vision, night blindness. (3) Growth lags behind that of normal children of the same age, anemia, wasting. (4) Recurrent colds, mouth ulcers, diarrhea. (5) Rough skin, hyperpigmentation, dermatitis. (6) Wounds that do not heal. There is a relative dynamic balance of elements in the human body, and deficiency or blind supplementation can break the normal balance and cause diseases. Therefore, it is necessary to conduct regular medical checkups for children to test trace elements, so as to detect, prevent and treat trace element deficiency early.