Nose bleeding may be caused by nasal cavity, sinus disease, but also some systemic diseases such as infectious diseases, cardiovascular disease, blood system diseases, etc., rather than a precursor of any disease. 1. Nasal cavity and sinus diseases (1) Nasal injury: nose suffered mechanical injury (such as bruises, nose picking, etc.), air pressure injury (such as in the process of diving, the air pressure difference between inside and outside the sinuses suddenly appeared to change, which can cause nosebleed), radiotherapy injury (head and neck radiotherapy) can cause nosebleed. (2) Nose – sinusitis inflammation: can be seen in acute rhinitis, atrophic rhinitis, sinusitis, diphtheria, nosebleed, can also be accompanied by runny nose, fever and other symptoms. 2. Systemic diseases Haemorrhagic fever, measles and other infectious diseases with bleeding tendency will appear nosebleed. Diseases of the cardiovascular system (e.g. high blood pressure, vascular sclerosis) can induce nosebleeds when they are emotionally agitated or over-excited. Hematologic system diseases (e.g., leukemia, thrombocytopenic purpura) can present with nosebleeds. There are many causes of nosebleeds, so it is recommended to go to the hospital in time to find out the cause and treat it promptly.