Why Does Sunlight Make Some People Sneeze?

Achoo! Most people sneeze after a tickling sensation finds its way up their nose, but for some, sunlight is another trigger. This is called the photic sneeze reflex, otherwise known as solar sneezing or ACHOO syndrome (which stands for Autosomal Dominant Compulsive Helio-Ophthalmic Outburst. Cute, right?).

Why People Are Talking About It

Somewhere between 18 and 35 percent of the population has this reflex, which is a genetic quirk—a dominant genetic trait, to be exact. It's been in our DNA a long, long time: the first reported case of this was recorded by philosopher Aristotle. In The Book of Problems, he wrote, "Why doth the heat of the sun provoke sneezing, and not the heat of the fire?" way back in 350 B.C.

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Why It Happens

Like so many strange things our bodies do, nobody knows why it happens, but we have some guesses. The most popular theory goes like this: the trigeminal nerve is the one responsible for making you sneeze when your nose is irritated. The optic nerve is responsible for constricting your pupils when you walk out into bright sunlight. These nerves are very close to each other, and it's possible that solar sneezing comes from an accidental crossing of the streams: your brain might be mistaking the optic nerve's signal that you've encountered bright sunlight as a signal from the trigeminal nerve saying there's something irritating your nose.

Why Do Some People Sneeze In Sunlight?

We don't know, but we sure can guess!

Guess What Else Can Make You Sneeze

Turns out that some people also sneeze when you turn OUT the light, if you catch our drift.

Written by Curiosity Staff December 12, 2015

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