Black pepper contains piperine, a chemical that triggers sneezing by irritating your nose.

Black pepper comes from the Piper nigrum plant and contains an alkaloid called piperine. This compound is responsible for the spice's characteristic heat and pungency. When peppercorns are ground, piperine molecules become airborne and enter the nasal cavity during inhalation.Once inside the nostrils, piperine interacts with the trigeminal nerve, which is responsible for sensation in the face. Specifically, it activates the TRPV1 receptors on the nerve endings. These are the same receptors that respond to heat and physical pain, signaling the brain that an irritant is present.The brain responds to this chemical irritation by initiating the sneeze reflex, also known as sternutation. This is a protective mechanism designed to expel foreign particles from the respiratory system at speeds up to 100 miles per hour. Research published in journals like 'Chemical Senses' has long studied how these specific alkaloids interact with human chemoreceptors.Interestingly, white pepper and green pepper also contain piperine but may cause less sneezing depending on how they are processed. Whole peppercorns are generally inert because the piperine is locked within the fruit's structure. Only when the physical barrier is broken through grinding or crushing can the chemical escape to irritate the nasal lining.