Why don't we sneeze when we sleep?

We put this question to Matt James, University of Bristol...

I work in the Department of Physiology and Pharmacology at the University of Bristol and my interest in sleep is in its role in cognition, so how a good night's sleep helps us to learn remember things well.

Well, this is a bit like asking if the tree falls in the forest but nobody's there to hear it because it makes a noise, so perhaps we do sneeze in our sleep but not enough to wake ourselves up regularly or to wake ourselves fully. And what really concerns me as a scientist is that no one's really done the experiment.

So, the first thing that springs to mind of course was that if it's really question, where is the evidence that we don't sneeze in our sleep? I've spoken to friends with hay fever and they reckon they do sneeze in their sleep on occasions.

It's firmly the case that, during sleep, we're less responsive to sensory input so we're less excitable. So if there is stuff around likely to make us sneeze, it's probably less likely to make us sneeze while we're asleep as evidenced by the fact that we're lying around not interacting with it much.

But, really, whoever asked this question should do the experiment to find a stimulus - some black pepper let's say - that makes you sneeze when you're awake, and then ask someone to waft it under your nose while you're asleep and see if it makes you sneeze or not!

Maybe it's just the change in thershold, maybe it just takes more pepper to make you sneeze when you sleep?