system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why does the body, as a self defensive response to some sicknesses, swell the nose so you can't breathe?
gpt
Swelling is part of the body’s response to fight viruses and other bad guys that try to make us ill. The swelling (inflammation) increases blood flow which brings tons of good bad-guy-fighting material (like white blood cells). It also increases heat to the area which helps speed up chemical reactions. 

Once the bad guys are caught, torn apart or moved, the next step is to get them expelled from the body (such as via pus, mucus or snot). 

Our nose swelling comes from irritation (eg blowing it a lot) but it doesn’t swell to stop us breathing. Our nose gets blocked because there’s some bad-guy-filled snot that needs gone. When there’s a lot of it it can cause some difficulty breathing.