Sneezing or or sternutation is a convulsive expulsion of air from the lungs rom the nose, generally at a speed greater than 60 mph. Each sneeze sends thousands of bacteria-laden droplets into the air, making it an effective spreader of germs and disease, such as the common cold.
Because the eyes and the nose are connected, it’s almost impossible for a person’s eyes to remain open while sneezing.
A sneeze is caused when the nerve endings of the mucous membrane in the nose are irritated, at which point a message is sent to the sneeze center in the brain, which sends a signal to the relevant muscles that affect the sneeze, expelling the irritation before any infection can result.Dust and pollen are the most common irritants, but any foreign particle can induce a sneeze. Most particles are harmless, but the body mistakes them for parasites and expels them to protect itself. Often the nose mistakes odors or cold air as potential invaders and this can also cause a person to sneeze. Some say that even an orgasm can bring on a sneeze.
Sneezing can also be caused by a swelling of the mucous membrane, which can happen when a person has a cold, for instance, while it’s also sometimes caused by sudden exposure to the sun or a bright light, a reaction known as the photic sneeze reflex.
Scientists don’t know exactly why this happens, but the close association between the nerves that cause the sneeze reflex and the eye’s optic nerve is thought to be a factor. About one in four people are photic sneezers and it is an inherited trait.
Source: http://unusualinfo.com/index.php/2015/06/07/why-do-people-sn. ..