Nosebleeds can be caused by nasal diseases or systemic diseases, such as: nasal septum diseases, nasal inflammation, nasal swelling, blood diseases, etc. 1. Nasal septum disease: deviated nasal septum, perforated nasal septum and other structural abnormalities can lead to nosebleed. 2. Nasal inflammation: Acute rhinitis, dry rhinitis, atrophic rhinitis and other diseases can also cause nosebleed, accompanied by dry nasal mucosa and nasal congestion. 3. Nasal swelling: hemorrhagic necrotic nasal polyps, nasal malignant tumors, hemangiomas, etc., can also cause nosebleeds. 4. Systemic diseases: AIDS, diphtheria, syphilis, leukemia, measles, scarlet fever and other diseases, can also cause nosebleeds. There are many reasons for nosebleed, if the phenomenon occurs for a long time, it is recommended that patients need to go to the hospital in time to improve the examination, give standardized treatment after a clear diagnosis, do not ignore the symptoms and delay the condition.