system
Given the following post, respond as if you're commenting on Reddit:
human
Why do people's noses get runny when they go out in the cold?
gpt
The blood vessels in your nose also expand to keep up with their job of warming up the air that you breathe in before it goes further down your respiratory tract. That in turn further activates your mucous producing cells, who among other things help moisten the air you breathe. All of this results in a runny nose!