There are several causes for the nosebleed including trauma (such as hitting the nose), fracture (nosebreak), altitude, severe stress, weakness of blood vessel, spontaneous hemorrhage among children, and hypertension among the elderly.
It normally stops when the blood clots, which may be encouraged by direct pressure. Medical opinion is divided on whether the best position to apply pressure is the bridge of the nose or the fleshy part. It is also undecided as to whether it is better to tilt the head forward during this procedure (to stop blood flowing back down the throat) or backward (to minimize the volume of blood in the nose).
Persistent epistaxis is an indication for urgent medical consultation.