Sneezing is called sternutation, and when you sternutate air rushes out your nose at a rate of 100 miles per hour!
Why pepper makes you sneeze:
Actually 2 reasons:
• First, most fine powders will stimulate the nerve endings inside the mucous membrane in your nose and make you sneeze.
• Second, pepper, be it white, black, or green, contains an alkaloid of pyridine called piperine. Piperine acts as an irritant if it gets into the nose. It stimulates (or irritates) the nerve endings inside the mucous membrane. This stimulation will cause you to sneeze. Actually, the nose wants to kick out this irritant and the only way it knows how to do this is by sneezing.
You don’t sneeze when you are asleep because the nerves involved in nerve reflex are also sleeping.