Do people sneeze in their sleep without waking up?

My old man was a snorer. His snoring was like the plot of a good action movie, with plenty of rising action. About 15 minutes after he'd fall asleep, it would sound like there was a heard of buffalo racing bulldozers and juggling chainsaws in my parents' bedroom. It would get louder and louder and then cut off when he finally woke himself up. There would be one final snort, and then a "huh?" After that, there was a small window of silence where the whole house could try and get back to sleep before the noise kicked back up.

You'd think it would follow, then, that we would regularly jar ourselves awake with sneezes, too, but that isn't the case. Actually, it seems I pulled a trick question out of the mailbag this week, because we don't sneeze in our sleep at all.

The Roots of the Sneeze

A sneeze is a reflexive response to external stimulants slipping past your nose hairs and reaching the sensitive mucous membranes that line the nasal passage (another common cause is the "photic sneeze reflex," a genetic trait that causes sneezing when a person is suddenly exposed to bright light). Nerve endings in the membranes send signals to the brain about the foreign invaders, and the brain sends signals to muscles in the face, throat and chest to go ahead clean house by expelling air from the nose and mouth.

We're actually more prone to sneezing while asleep, since the mucous membranes swell when we lie down, but because there usually isn't much airflow or movement to stir up dust or other particles while we sleep, the membranes don't come into contact with as many stimulants as they do when we're awake.

Our odds of have having to sneeze during sleep are already reduced, but our bodies have a neat little trick up their sleeves to keep us at rest. It's called REM atonia, a state caused by the shutdown of the release of certain neurotransmitters during REM sleep that results in motor neurons not being stimulated and reflectory signals not being sent to the brain. So, even if there were various stimulants being kicked up while you slept (say, by an evil cat playing with his rubber ball or biting your toes at five in the morning), and a few got into your nose, the brain wouldn't be alerted to the matter.

It is possible, if the external stimulants are sufficient (say, by an evil cat dusting your mustache with pepper), for a person to wake up to sneeze.

This question was asked by Regina from Texas. If you've got a burning question that you'd like to see answered here, shoot me an email at flossymatt (at) gmail.com. Twitter users can also make nice with me and ask me questions there. Be sure to give me your name and location (and a link, if you want) so I can give you a little shout out.