An interesting phenomenon is that about 1/3 of people, when exposed to sudden light, especially sunlight, start to sneeze. Among the scientific fella, this phenomenon is known as photic sneeze reflex. It occurs in about 35 percent of the world population, making it very common. Although this genetic peculiarity is not yet fully explained by the scientific world, there is some scientific explanation behind it!


photic sneeze reflex

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Aristotle studied why some people sneeze when looking at the sun. He explained that it’s as a nose reflex, triggered by the sun’s heat. That the rapid warmth, felt by the nose, is what causes the photic sneeze reflex.

Francis Bacon also studied this reflex. He thought that the sudden exposure to sunlight causes tears in the eyes, which successively irritate the nose and provoke sneezing.

Scientific Explanation Of Photic Sneeze Reflex

When talking about photic sneeze reflex, modern science has its own opinion as well. Research shows that sneezing happens too fast after being exposed to light, to be the result of tears. This is when neurology takes its turn in explaining the phenomenon. Namely, many experts agree that when people get exposed to direct light, some wires cross inside their brains, triggering the photic sneeze reflex.

Sneeze is an involuntary air expulsion from the nose and the mouth, caused by a nose irritation. This irritation is felt by the trigeminal nerve, which is a cranial nerve, responsible for the motor control and sensation of the face. It’s located right next to the optic nerve, which senses the light signals that enter through the retina. The theory is that when the optic nerve sends signals to the brain to tighten the retina, due to the sudden exposure to light, some of those signals are also sensed by the trigeminal nerve. When sent to the brain by the trigeminal nerve, these signals are mistaken and incorrectly processed as a nose irritation. Thence the sneeze.

Aristotle’s and Bacon’s theories were not entirely wrong. This sneezing phenomenon is indeed connected to the nose!

An interesting fact here is the hereditary factor. Namely, if one parent sneezes when looking at bright light, about half of the offspring will experience the same.

The photic sneeze reflex is not related to any pathological conditions. Thus, scientists don’t spend too much time on confirming its exact cause with scientific evidence. So, if you sneeze when exposed to a sudden light source, don’t worry. It’s nothing harmful and about a third of the world population is doing just the same!

Reference:
Looking at the Sun Can Trigger a Sneeze