It is rare for a person to sneeze during sleeping hours. Sneezing appears as a protective response to a stimulus of the nasal mucosa, which is generally triggered by particles that leak into the respiratory passages. In order for neurons to secrete the neurotransmitters that command the action of sneezing, the stimulus has to reach the brain stem.
However, while we sleep, especially during deep or REM sleep, which is characterized by rapid movement of the eyes, the activity of numerous brain systems declines, and the reflex arc is not completed. This means that, even if the stimulus occurs, the sneeze does not occur, since the neurotransmitters are deactivated.
However, when the stimulus is very intense – for example, if there is smoke in the environment or a feather is passed through the nose – the alert systems are activated.
