When patients have nosebleeds at night, the causes are nasal mucosa and submucosal vascular erosion and rupture, nasal septal deviation, systemic diseases, etc., as follows: 1. Nasal mucosa and vascular erosion and rupture: The most direct cause is the occurrence of nasal mucosa and submucosal vascular erosion and rupture. This condition may be related to excessive dryness of the nasal mucosa, and may also be related to the existence of inflammatory infectious and allergic diseases of the nasal cavity and sinuses. 2, nasal septal deviation, nasal foreign body: some patients may have a significant deviation of the nasal septum, or the further emergence of hemangiomas, bleeding polyps and other bleeding-prone growths in the nasal cavity, which can easily cause the occurrence of nosebleed symptoms. 3, systemic diseases: Some patients may be affected by systemic disease factors, such as hypertension, diabetes, liver and kidney diseases, blood system diseases, etc. If the symptoms of nosebleeds recur, further detailed examination is needed to help clarify the cause.