Frequent nosebleeds from the left nostril may be caused by environmental dryness, or dry rhinitis, nasal polyps, nasal septum deviation, and so on. 1. Environmental dryness: If you live and work in a dry environment for a long time, you may experience nasal mucous membrane cracking and bleeding, which may lead to frequent nosebleeds from the left nostril. 2. Dry rhinitis: mainly due to the reduction of nasal gland secretion, the nasal mucosa is dry, there may be nasal crusting, localized cracking and bleeding, which may lead to the appearance of the left nostril often nosebleed. 3. Nasal polyps: hemorrhagic necrotizing nasal polyps in the growth, may lead to the appearance of the left nostril often nosebleeds. 4. Deviated nasal septum: The growth of nasal septum spines or the obvious curvature of nasal septum leads to thin mucous membrane, which is prone to frequent rupture of blood vessels at the tip of spines and submucosal vasodilatation, which may lead to frequent nosebleeds from the left nostril. It is recommended to consult a doctor as soon as possible for a clear diagnosis of frequent nosebleeds from the left nostril.