There are several causes of nosebleeds in children. One, it is due to dry air, not enough humidity inside the room and increased brittleness of the nasal mucosa causing bleeding. Secondly, nosebleeds are caused by children’s bad habit of picking their nostrils. Third, if children have a cold, the nasal mucosa can be infected with bacteria and viruses, which can also destroy the blood vessels and cause bleeding. Fourth, the cause of nosebleeds in children may also be some systemic diseases, including thrombocytopenia syndrome and hemophilia, as well as coagulation disorders and other diseases. If children have leukemia, some of them will also have nosebleeds. All of these need to be examined by a specialist in a hospital for a clear diagnosis before they can be treated regularly.