Dry air can sap moisture from nasal membranes. Not only is it uncomfortable, but it cause the mucous lining of the nose to crust, crack, and bleed–sometimes without any provocation. But nosebleeds are most often due to nose picking or some other disturbance, such as an aggressive nose blow or the repeated poke of a nasal spray bottle. Inflammation due to allergies or common viruses like colds can also make the nasal lining more vulnerable to nosebleeds.

Less often, a bloody nose is the consequence of blunt trauma due to, say, a car accident or a punch. Sometimes blunt trauma causes nosebleeds when children stick small objects up their noses or when adults try to extract those items. Using certain allergy medications or illegal drugs like cocaine can cause nasal bleeding too.

In rarer cases, nosebleeds can also be caused by a genetic condition called hereditary hemorrhagic telangiectasia, a blood clotting disorder, or even cancer.