"Cool the head and warm the feet" From the perspective of modern medicine, the head is close to the heart, and the supply of energy and nutrients is sufficient. About 1/3 of oxygen in human blood is supplied to the head and brain; The feet are far away from the heart, so the body energy and nutrients can't be delivered in time. So if the feet are warm, it can accelerate the blood circulation of the whole body and ensure the timely supply of nutrients. For infants and young children, they don't know how to express that they are too warm or too cold, so they don't have to dress like steamed zongzi at first. There is a folk saying that "if a child is safe, it often brings three points of hunger and cold." The old, the weak, the sick and the disabled may have poor tolerance to cold and heat, so they should be carefully conditioned and cannot be treated like ordinary people. For example, the respiratory tract of elderly patients with chronic bronchitis is easily stimulated in cold weather, which can induce spasm of trachea, bronchi or bronchioles and cause recurrence or aggravation of diseases such as chronic bronchitis and bronchial asthma. Therefore, we should pay special attention to the warmth of the head and neck, and tie a thin scarf if necessary.