Anal bleeding is a symptom of a disease, rather than a disease itself. The bleeding can occur as the result of a number of different conditions, some of which are life threatening.
The most common cause of anal bleeding is hemorrhoids. However, there are also other, more serious causes. So while the cause of the bleeding may or may not be serious, locating the source of any type of gastrointestinal bleeding is still important.
For more information on this topic, see the full eMedTV article on Anal Bleeding.