Nosebleeds can be caused by physiological factors such as dryness of the nasal passages and forcefulness of nose blowing, as well as diseases such as deviated nasal septum and rhinitis. 1. Physiological factors: If the mucous membrane of the nasal cavity is too dry, the nasal mucous membrane may be damaged when blowing the nose, resulting in nosebleeds. Secondly, if you blow your nose too hard, capillary rupture may lead to nosebleeds, which is a physiological phenomenon. 2. Deviated nasal septum: Deviated nasal septum means that the nasal septum is deviated to one side or both sides, and the patient will suffer from nasal congestion, headache, thinning of nasal mucous membrane, and increase of blood vessel brittleness, and some of the patients will suffer from nosebleed when blowing their noses. 3. Rhinitis: Rhinitis is mainly caused by bacteria, viruses or allergens, etc. Patients will experience symptoms such as nasal congestion, itchy nose, runny nose, etc., and a few patients will experience nosebleeds. There are more reasons for nosebleed caused by blowing the nose, and patients are advised to go to the hospital for examination and clear diagnosis. If it is caused by diseases, you need to cooperate with doctors to standardize the treatment.