Why does a cold causes blood vessels in the nasal passages to swell and, as a result, a stuffy nose?

Question

I’m aware a stuffy nose is caused not by mucus, but by “swollen blood vessels in the nasal passages”. But why does such swelling happen? How exactly does a cold causes this?

In: 18

Answer 1

ELI5 version: Cold air makes your nose try to warm the arm.

ELI20: cold causes mast cells to do a histamine release which causes your blood vessels to become leaky, causing increased swelling which then warms the air due to increased blood flow.