5-year-old children have nosebleeds, including the following causes: 1, congenital developmental abnormalities: during development, due to changes in the vascular structure caused by nasal septal deviation and abnormal development of blood vessels in the Ri area of the nose; 2, medical diseases: such as benign blood system diseases, idiopathic thrombocytopenic purpura, malignant blood system diseases leukemia, which require medical treatment; 3, dry air: in winter, especially in the north after heating the air is dry The air is dry, leading to dry nasal mucosa, blood vessel rupture and bleeding. Do not be overly concerned, the home properly placed humidifier to make the air moist, can avoid rhinorrhea.