system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the warm, humid air of a shower "open up" my sinuses, yet the cold, dry winter air also "opens up" my sinuses.
gpt
They both work in different ways. The humidity of the shower wets the mucus that coats your sinuses, allowing it to flow better and making it less viscous. The cold dry air stimulates the flow of mucus, a normal physiologic response to prevent nasal dryness. The cold air can also constrict blood vessels in your nasal cavity, which has the effect of expanding the interior nasal airway and bringing down tissue swelling.