Epistaxis, or a nosebleed, is the relatively common occurrence of hemorrhage from the nose, usually noticed when the blood drains out through the nostrils. There are two types: anterior (the most common), and posterior (less common, more likely to require medical attention). Sometimes in more severe cases, the blood can come up the nasolacrimal duct and out from the eye. Fresh blood and clotted blood can also flow down into the stomach and cause nausea and vomiting. It is rarely fatal, accounting for only 4 of the 2.4 million deaths in the U.S. in 1999. The causes of nosebleeds can generally be divided into two categories, local and systemic factors, although a significant number of nosebleeds occur with no obvious cause. Nosebleeds are due to the rupture of a blood vessel within the richly perfused nasal mucosa. Rupture may be spontaneous or initiated by trauma.
Contributions by Jfdwolff, Rls, and Arcadian.