Why Do We Sneeze?

Have you ever wondered why we sneeze? Let's get to the bottom of this.

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When the tiny hairs in your nose sense a foreign contaminant, they send a message to the brain stem which triggers a series of reactions to close your eyes, mouth and throat to build up pressure behind the vocal chords, then your chest muscles contract fast and hard, causing air, saliva and mucus to shoot out of your nose and mouth at speeds close to 100 mph (160 kph). The process, known medically as sternutation, is better known to us as sneezing, and is an effective way for our body to remove potentially harmful bacteria and viruses.

It's not just nasal contaminants that make us sneeze: Sunshine can trigger 10 to 35 percent of the population to sneeze. Scientists believe the nerve which connects the face to the brain, runs next to the optic nerve, and when the retina is flooded with light the signal can cross over to the trigeminal nerve and trigger a sneeze. The tiny hairs, or cilia, in the nose stay active for a few minutes after you sneeze, which is why sometimes sneezes come in twos or threes.

Do you sneeze in even or odd numbers? Some think the number of times you sneeze is actually genetic! Let's hear about your sneezing habits in the comments below.

Learn More:
Localization of the "sneeze center" (via Neurology.org)
"The existence of distinct sneeze-evoking centers in the brainstem has been demonstrated in cats, represented bilaterally along the ventromedial spinal trigeminal nuclei and in the adjacent pontomedullary lateral reticular formation."

Why do we sneeze? (via Scientific American)
Sneeze: to make a sudden violent spasmodic audible expiration of breath through the nose and mouth, especially as a reflex act.