The inside of the nose is covered with moist, delicate tissue (mucosa) that has a rich supply of blood vessels near the surface. When this tissue is injured, even from a minor nick or scratch, these blood vessels tend to bleed, sometimes heavily. Nosebleeds near the front of the nose, called anterior nosebleeds, are very common since this is the most accessible area to injury. The most frequent location is the nasal septum, the wall between the two sides of the nose. In most cases, this type of nosebleed is not serious. It usually can be stopped with some local pressure and a little patience.
Only rarely is a nosebleed life threatening or fatal. In these cases, the hemorrhage (severe bleeding) is usually from an artery in a posterior location, higher and deeper in the nose. Posterior bleeds usually drain down the back of the throat, but can also bleed out of both nostrils. Also, in most cases of severe nosebleeds, the person has another health problem, such as high blood pressure or a bleeding disorder, or the person takes a blood-thinning medication that slows down the blood-clotting process.
Certain people are more likely to get nosebleeds because of their environment, work history, health problems or use of medications that increase the tendency to bleed. Common risk factors for nosebleeds include:
A hot, dry indoor climate - This is a trigger for nosebleeds in parts of the United States where heat (especially forced hot air) is used during the winter. The hot, dry indoor air causes the delicate nasal skin to crack and bleed. Nosebleeds are more frequent during changes of seasons before the tissues have become accustomed to the change in humidity.
A deviated septum - If the wall between the two nostrils is shifted to one side (deviated), air flow in the nostrils is uneven. The altered airflow pattern causes the skin of the nasal septum, on the narrower side, to become dry and cracked, increasing the risk of bleeding.
Colds and allergies - Upper respiratory tract infections and allergies cause inflammation in the nose, which can increase the risk of bleeding. More congestion can cause blood vessels to widen (dilate), which makes them more vulnerable to injury. Strenuous nose blowing to clear the nose also can cause a nose to bleed or to start bleeding again after a nosebleed has been controlled.
Exposure to irritating chemicals - The primary culprit is cigarette smoke, even secondhand cigarette smoke. Workers also may develop nosebleeds from on-the-job exposure to sulfuric acid, ammonia, gasoline or other chemical irritants.
Medical conditions - Examples include kidney failure, thrombocytopenia (low levels of the blood platelets needed for clotting), high blood pressure and hereditary bleeding disorders, such as hemophilia.
Heavy alcohol use - Alcohol interferes with the normal activity of platelets in the blood, and this increases the time needed for blood clots to form. It also makes superficial blood vessels dilate (enlarge), making them more likely to be injured and bleed.
Medications that interfere with blood clotting - These include prescription blood-thinners (anticoagulants) and nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen (Aleve, Motrin and others).
Homeopathic medications and dietary supplements - Some dietary supplements contain chemicals that prolong bleeding similar to prescription blood thinners. Danshen, dong quai, feverfew, garlic, ginger, ginko biloba, ginseng and vitamin E are some of them.
Nosebleeds also commonly are caused by trauma, such as nose picking, forceful blowing of the nose or severe facial trauma from an automobile accident or contact sports.