Asked by: Seonaid Johnston, Perth
Even if an insect crawled across your nose,you probably wouldn’t sneeze while dreaming. During REM sleep (the phase where dreams take place), your muscles are paralysed so that you don’t thrash around and hurt yourself. This paralysis extends to reflex muscle contractions, so you can’t sneeze while you are dreaming. In non-REM sleep your muscles are free to move again but the trigeminal motor neurones responsible for triggering a sneeze are still suppressed. It is just about possible to sneeze during this non-REM sleep, but the exertion will normally wake you up.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.