Why do we sneeze?

A sneeze begins when irritants — dust, pollen, pepper, or a virus — stimulate the sensitive lining of the nose. Nerve signals travel to the brainstem, which triggers a coordinated burst: a deep breath, a build-up of pressure, and an explosive release through the nose and mouth to clear the airway. The expelled air and droplets can travel several feet and, by some measurements, move at speeds approaching 100 miles per hour. Sunlight makes some people sneeze too — an inherited trait called the photic sneeze reflex that affects up to a quarter of people.