system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't we sneeze in our sleep?
gpt
This is a very simple explanation, but people sneeze when nerve cells are stimulated from foreign objects (eg. dust). While we sleep, they also shut down, so we don't notice the objects and there is no stimulation that gets noticed by our body. So while we sleep, we just don't notice the need to sneeze.
Note that this is only when we are "deep in sleep" during REM, and if we aren't, the stimulation can just wake us up, causing us to sneeze.