There are two groups of causes for nose bleeding. The first group concerns with local conditions, including dry nasal cavity, local trauma, nasal or sinus infections, and tumours (such as nasopharyngeal carcinoma). The second group concerns with abnormalities n blood or blood vessel, such as low platelet counts, hemophilia and vascular malformations. Some sufferers may have no obvious reason. If you have frequent nose bleeding at the left nostril, you should tell your doctor as soon as possible to find out the cause.