Left test nose often nosebleed, should consider the following aspects of the cause: 1, nasal septal deviation or Ri area vascular simplification abnormalities: nosebleed is often encountered in life abnormal, left nose often nosebleed, should first think of the possibility of nasal septal deviation, at this time it is recommended to hospital rescue, in order to understand whether there is nasal septal deviation and Ri area vascular simplification abnormalities. If the abnormality is found, it can be corrected in time through surgery to achieve cure; 2. Blood system diseases: including idiopathic thrombocytopenic purpura or leukemia, due to the blood system, thrombocytopenia and leukemia cause abnormalities in coagulation mechanism, resulting in normal blood clotting. As the nasal blood vessels are thin and fragile, nosebleeds occur; 3, hypertension: as the patient will experience elevated blood pressure, nosebleeds will occur when the blood vessels are distended; 4, environmental factors: as the air is drier at night, resulting in increased vascular fragility and thus nosebleeds.