Why Don't We Sneeze When We Are Asleep?

Sneezing, is as stated in the previous post, is a reflex action in response to stimulus in the nasal passage to the brain.  During sleep, most of the activity of the brain declines we are less responsive to external stimuli and the reflex action is not initiated. As such sneezing does not take place during sleep. But if the stimulus is very intense, it can waken the brain and sneezing will occur and you will wake up.