Nosebleeds, or epistaxis, are a common phenomenon experienced by approximately 60% of individuals at some point in their lives. The causes of nosebleeds can be attributed to various factors, including local conditions, systemic issues, and environmental influences. Local causes of nosebleeds commonly include nasal inflammation, tumors, trauma, foreign bodies, and a deviated septum. These factors can lead to bleeding from the nose, which may present as minor bleeding, blood-streaked nasal discharge, or blood in phlegm upon waking. In severe cases, bleeding may be substantial, flowing from the nostrils or into the throat, resulting in hemoptysis. Local causes are often accompanied by additional symptoms such as nasal congestion, runny nose, headache, or reduced sense of smell.

Systemic factors that can lead to nosebleeds include unstable blood pressure, hypertension, and increased venous pressure. Increased venous pressure is commonly seen in conditions like cor pulmonale, chronic bronchitis, and masses in the thoracic cavity, mediastinum, or neck that compress the venous system, thereby affecting venous return from the head and face. Coagulation disorders, such as thrombocytopenia seen in conditions like purpura or leukemia, can also cause nosebleeds. Febrile illnesses, including various infections and rheumatic fever, can accelerate blood circulation and dry out nasal mucosa, leading to bleeding. Liver dysfunction, such as chronic hepatitis or cirrhosis, affects the production of clotting factors and increases the risk of nosebleeds. Kidney diseases, such as chronic nephritis or renal failure, can lead to chronic vascular damage and abnormal coagulation mechanisms, resulting in bleeding. Additionally, diseases related to menstrual cycles and estrogen levels can also cause nosebleeds. Hereditary bleeding disorders, such as hereditary hemorrhagic telangiectasia, involve abnormal dilation of capillaries in the nasal septum and can lead to nosebleeds. Certain medications, including anticoagulants and long-term low-dose aspirin use, can prolong clotting time and cause nosebleeds.

Nosebleeds due to systemic factors are often accompanied by symptoms related to the underlying condition. For instance, thrombocytopenia can cause not only nosebleeds but also skin purpura. Chronic hepatitis or cirrhosis may present with spider angiomas and vascular dilation. In summary, nosebleeds can be an indication of various underlying health conditions.