Left nose bleeding may be caused by environmental dryness, may also be triggered by nasal hemangioma, nasal septum deviation and other diseases, caused by nose bleeding of many diseases, can not be predicted by nose bleeding is which specific disease. 1. Dry air: in dry air environment, nasal mucous membrane is easy to be dry, and capillary wall may rupture and bleed. 2. Nasal hemangioma: Nasal hemangioma is a benign tumor of the vascular tissue, which occurs on the mucosal surface of the nasal septum. When the tumor grows on the left side of the nasal septum and protrudes on the mucosal surface, it may bleed after cracking and ulcerating on the surface. 3. Deviated nasal septum: when the nasal septum is deviated to one side to form a splinter or the mucous membrane is thin, nosebleed can occur. If the left side of the nose bleeds for a long time or repeatedly, it is recommended to consult a doctor in time for systematic examination and clear diagnosis.