Nosebleeds may be caused by environmental factors, bad habits, trauma, deviated nasal septum, inflammation of the nasal cavity and thrombocytopenia. 1. Environmental factors: the air is dry and the amount of water you drink is low, leading to dry nasal mucosa and capillary rupture causing bleeding. 2. Bad habits: often digging the nostrils with the hands, pulling out the nose hairs, may cause damage and bleeding. 3. Trauma: when you are hit by external force, the blood vessels in the nasal cavity rupture and cause bleeding. 4. Deviated nasal septum: Nosebleeds can occur when the structure of the nasal septum is abnormally deviated to one side. 5. Nasal inflammation: acute rhinitis, chronic rhinitis, dry atrophic rhinitis, etc. can cause nosebleeds. 5. Thrombocytopenia: for example, secondary thrombocytopenia, idiopathic thrombocytopenic purpura, etc., can cause thrombocytopenia leading to nosebleeds. Nosebleed may also be other reasons, it is recommended to consult a doctor in a timely manner, and follow the doctor’s instructions for treatment.