Nosebleed: Causes and symptoms

Cancers are an uncommon cause of nosebleeds, but by far the most serious. Injury from fists, fingers, and over zealous nose blowing leads the list. Tumors from the front of the brain may break through into the sinuses or the back of the nose. Bleeding may be a trickle or a flood.

— J. Ricker Polsdorfer, MD