There are numerous causes and conditions that are associated with the development of nosebleeds.

 
In some cases, there may be no readily identifiable cause of epistaxis:
  • Local trauma - Local trauma is the most frequent cause of nosebleeds. Local trauma may occur from insertion of objects in to the nose, most commonly fingers.
  • Insertion of foreign bodies into the nose is also a common cause, especially in children.
  • Facial trauma - Falls and accidents causing trauma to the face, especially associated with broken bones, can cause significant bleeding.
  • Nasal/Sinus infections - Infection can cause vessels in the nose to bleed. Sinus infections may cause frequent bouts of sneezing and frequent blowing of the nose,
    both of which may cause bleeding by increasing the pressure in these vessels.
    Common colds and allergic rhinitis are also associated with epistaxis.
  • Oral anticoagulants - Medications like Warfarin (Coumadin), used to prevent blood
    clots from forming, are a frequent cause of nosebleeds.
  • Coagulopathy - Several conditions are known to predispose to epistaxis, such as
    sphlenomegaly, thrombocytopenia, platelet disorders, and other bleeding disorders, such as Von Willebrand’s disease and hemophilia. These conditions may affect the
    body’s ability to form blood clots necessary to stop bleeding when it occurs.
  • Hypertension - Nosebleeds are more common in people who have high blood pressure, although hypertension is not thought to be a direct cause of epistaxis.
  • Vascular abnormalities - There are several conditions that affect blood vessels that may predispose to nose bleeds. Some of these conditions include having sclerotic
    vessels, hereditary telangiectasia, and AV malformation (arteriovenous malformation).
  • Neoplasm - Cancerous tumors of the nasal cavity may cause bleeding to occur if the tumor erodes into blood vessels.
  • Septal perforation/Deviation - Abnormalities of the septum cause uneven air flow between the nostrils, causing one nostril to receive more air, which may lead to dryness and cracking of nasal tissues.
  • Endometriosis - Although uncommon, endometriosis can cause nosebleeds if endometrial patches seed in the nasal passages.
  • Dry/Heated Air - Having a bloody nose is much more common in the winter due to low humidity and dry air. Dry, hot, low-humidity climates cause the same problem, which is the drying out of nasal tissue, which in turn causes the tissue to crack or crust. Rubbing, picking, or blowing the nose causes this delicate tissue to bleed.
  • Chemical Irritants - The use of cocaine or inhaling chemical irritants can cause a bloody nose.
  • Heavy Alcohol Use - Using alcohol regularly can cause blood dyscrasisas that may cause bleeding.
  • Homeopathic Medications - There are several homeopathic remedies and dietary supplements that that are associated with higher risk of bleeding. Some of these include feverfew, ginger, don quai, vitamin E, gingko biloba, garlic, danshen, and ginseng. Many people take these supplements and are not aware that they can contribute to a bloody nose.
  • Pregnancy - The condition of pregnancy causes blood vessels to expand. Additionally, pregnancy causes a higher blood volume, which can increase pressure on already dilated blood vessels.