Apr 1, - Nosebleeds are most often a result of dryness in the air from indoor heat. Click to learn more about causes, prevention, and treatment. Sep 14, - The lining of your nose contains many tiny blood vessels that lie close to the surface and are easily damaged. The two most common causes of nosebleeds are: Dry air — when your nasal membranes dry out, they're more susceptible to bleeding and infections. Nose picking.