Nosebleeds in children may be caused by trauma, disease, environment, personal habits and other factors. 1. Trauma: children may be caused by nose picking, blowing, collision bleeding phenomenon, mainly due to the more fragile nasal mucosa, nasal mucosa is more fragile, after external stimulation will cause capillary hemorrhage, so the phenomenon of nosebleed. 2. Disease: Diseases in the nasal cavity can lead to the phenomenon of nosebleeds, in which nasal mucous membrane erosion, nasal vascular malformation is the main reason, but also may be leukemia, leukemia due to the abnormal coagulation function, which can cause symptoms of nosebleeds. 3. Environment: the weather is dry or in the air-conditioned room for a long time, the moisture content in the air will be reduced, the nasal cavity will become dry, the nasal mucosa produces dryness, easy to rupture the phenomenon, and thus appear nosebleeds. 4. Personal habits: some babies like to repeatedly pick their noses, resulting in damage to the nasal mucosa, there will also be nosebleeds. It is recommended to go to the regular hospital for examination, the doctor will be based on clinical symptoms to give judgment, clear cause of timely targeted treatment.