A 4-year-old child with small red spots all over his body may be caused by rubella, chicken pox, eczema and so on. 1. Rubella: Rubella virus mainly exists in the respiratory secretions of the patient, spread through coughing, sneezing or direct contact and other ways, resulting in small red spots all over the body of a 4-year-old child and accompanied by sore throat, runny nose and other symptoms. 2. chickenpox: the virus enters the human body in the respiratory mucosa local proliferation and enter the bloodstream to form the initial viremia, will spread to the epidermal keratinocytes and mucosal epithelial cells, resulting in small red spots all over the body of the child, some patients may also appear herpetic chickenpox, hemorrhagic chickenpox and other manifestations. 3. Eczema: when the patient is affected by abnormal immune function, skin barrier dysfunction, allergic substances induced by factors such as the emergence of small red dots all over the body, appearing self-conscious itching and other symptoms. In addition to the above, it may also be the more common scarlet fever, measles, hand, foot and mouth disease, parents are advised to take their children to the hospital in a timely manner, under the guidance of the doctor, relevant examinations, according to the specific results of the examination, to take targeted treatment.