system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why does my nose run when it's cold outside?
gpt
Our noses warm and humidify — add moisture to — the air we breathe as it travels down into the lungs. So when you inhale cold, dry air, the moist tissue inside the nose automatically increases fluid production to do its job of protecting sensitive lung tissue. But when there's too much fluid, the excess tends to drip out, creating a runny nose.