system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we only sneeze when we're awake?
gpt
Do we?

Regardless, the most likely answer is sleep paralysis. When you sleep your brain essentially "shuts off" most of your muscles so you don't hurt yourself when you move in your dreams. The muscles responsible for sneezing are partially voluntary (the diaphragm, abdominal muscles, etc.) which would be subject to the paralysis and thus wouldn't work when you need them to sneeze.

*However*, portions of the diaphragm are also involuntary and do not get turned off when you sleep (else you wouldn't be able to breathe). And considering the generally reflexive nature of sneezing I'd hazard a guess that we in fact are still able to sneeze while asleep. It's probably just uncommon because you're not breathing as deeply so there's less particulate matter getting sucked into your nasal passages that would trigger the reflex.