Sudden nosebleeds without signs may be related to deviated nasal septum, nasal capillary hemangioma, dry rhinitis and other factors. 1. Deviated nasal septum: Sudden nosebleed without signs may be related to deviated nasal septum, the mucous membrane on the deviated side is thin, blood vessel dilation is obvious, and it is easy to be stimulated by the outside world, and sudden nosebleed without signs occurs. 2. Nasal capillary hemangioma: this disease mostly occurs in the front of nasal septum, the front of inferior turbinate, external nasal skin, etc., the volume is small, the diameter is more in 1.5cm or less, often for the polyp-like with the tip, the surface is smooth or forming ulcers, and it is easy to happen the symptom of nosebleed suddenly and without any sign. 3. Dry rhinitis: this disease often has nasal dryness, nasal itching, nasal congestion, nasal bleeding and other symptoms. Nasal cavity inspection can be seen mucous membrane slightly pale, dry, viscous secretion or thin crust attached to the front of the nasal cavity, and the mucous membrane of the anterior nasal septum appear erosion, superficial ulceration, may appear suddenly without warning nosebleed. If you have a nosebleed suddenly and without warning, you should go to a regular hospital in time for a systematic examination to clarify the diagnosis and cause of the disease.