Why's it the fact that your nose starts to bleed when the air is dry?

Dried out mucosa: The lining of your nose, or mucosa provides moisture to the dry air you breathe to condition the air before it reaches the lungs. When the air is really dry, the mucosa can dry out, crack and bleed causing a nose bleed. Treatment involves pressure to stop the bleeding, followed by moisturizing with nasal saline, saline gel, or ointment. Medical problems can cause chronic bleeds requiring an ent.