Why can’t sneeze in your sleep

　　Sneezing is usually the process of clearing irritants from the nose and throat. When a foreign object enters the nasal cavity, passing through the nasal mucosa, it may trigger the release of a neurotransmitter called histamine.
　　Histamine consists mostly of nitrogen particles that irritate nerve endings in the nasal mucosa, causing them to swell and send signals to the brain, which in turn causes sneezing by sending signals to the pharyngeal and tracheal muscles to dilate the nasal passages and throat. There are 4 stages of human sleep, and people who are sleeping are usually in the stage of rapid eye movement sleep. At this stage, our muscles are in a relaxed state, and the neurotransmitters will be turned off. Even if allergens or other particles enter the nasal cavity and reach the mucous membranes, the histamine neurotransmitters will not be triggered, so people will not sneeze. During non-REM sleep (light sleep), areas of the cerebral cortex and thalamus are constantly activating each other to suppress sensory responses such as sneezing, so we don’t normally sneeze during light sleep. But if the external stimulus is strong (such as a sudden large amount of dust in the air), then the person may wake up and then sneeze.