These two things work together nose picking occurs more often when mucus in the nose is dry and crusty. Other, less common causes include injuries, colds, allergies, or cocaine use. The cause of nosebleeds often can t be determined. The nose has many blood vessels in it to help warm and humidify the air you breathe. The vessels lie close to the surface making them easy to injure.
Most nosebleeds occur in the front part of the nose and stop in a few minutes.
A few nosebleeds stem from large vessels in the back of the nose. These nosebleeds can be dangerous. They may occur after an injury. You ll need to get medical attention if a nosebleed goes on for more than 15 minutes or if it occurs after an injury, such as a punch in the face, especially if you think you may have a broken nose. A nosebleed after a fall or car wreck could be a sign of internal bleeding.