The causes of inexplicable nosebleeds may include dry nasal mucosa, rhinitis-sinusitis, and blood clotting disorders. 1. Nasal mucous membrane dryness: dryness may lead to nasal mucous membrane dryness and nasal capillary rupture caused by nosebleeds. 2. Rhinitis – sinusitis: may make the nasal mucosa vasodilatation, mucosal fragility increased, thus causing capillary rupture nosebleed. 3. Coagulation dysfunction: If there is thrombocytopenia or abnormal coagulation function, there will be oozing of blood from the nasal mucous membrane tissue and nosebleed. Inexplicable nosebleeds may also have other causes, such as nasal septum lesions, liver and kidney dysfunction, blood disorders, etc., should be timely to the hospital, the doctor according to the symptoms, signs and auxiliary examination to determine the specific cause of the disease.