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The reason you sneeze when you look at the sun

Are you one of those people who, for some reason you’ve never really understood, always sneezes when you look at bright lights?

It could be while you’re driving and you emerge from a tunnel, or every time you come out from the office into the daylight in your lunch break.

Well, the good news is you’re not alone, and there’s actually a name for your bizarre sneezing habits. About one in four of us ‘suffer’ from ACHOO – ‘autosomal dominant compelling helio-ophthalmic outburst’ syndrome.

Now that’s a lot of confusing words, so let’s break it down.

Autosomnal dominant: If you’re one of these people, well, you can blame your parents. While scientists are yet to isolate the gene, most of the research suggests that it’s ‘autosomnal dominant’ – meaning it’s a genetically transmitted syndrome.

If one of your parents has it then there’s a 50/50 chance you’ll have it as well.

Compelling: Now here is where the doctors who came up with the acronym basically just needed to find a way to fit in the letter ‘C’. It’s ‘compelling’ because it affects different people to differing degrees. Not really what they word compelling means, but hey, they’re scientists not authors.

Helio-Opthalmic: Helio comes from the Greek word for ‘sun’ and opthalmic refers to the eye, because your sneezing is triggered when your look into the sun or other bright lights.

Outburst: …an outburst. They could have used the word sneeze here but ‘ACHOS’ just doesn’t have the same ring to it.

Basically what’s happening is that the optical stimulation of the eye from bright lights is triggering the sneeze reflex in your brain. But that’s about all we know for certain, we don’t know why the stimulation causes that reaction.

One theory is that the eyes and nose are connected through the trigeminal nerve, which is responsible for motor functions in your face and the stimulation of the eye is relayed to the nose.

Another theory is a process called “parasympathetic generalisation”, which is when one part of your parasympathetic nervous system (responsible for activities when your body is resting) is stimulated, the other parts are also activated. So it’s been hypothesised that when you squint or shut your eyes in bright light, it might indirectly create nasal mucus which then makes you sneeze.

Now all of these might seem trivial, but the ACHOO syndrome can actually prove quite dangerous – momentary blindness when you’re driving can be deadly, with a UK study finding that sneezing is behind roughly two million cases of dangerous driving annually.

Also, if you’re a high-wire acrobat or a cricketer looking into the sun to catch a ball on the boundary, a sun-triggered sneeze could prove quite painful or at the very least, incredibly embarrassing.

So what can you do to avoid the scourge of ACHOO?

Live in a cave and never expose yourself to the light of day. Or just wear polarised sunglasses.

About the author

Riordan is Techly’s News and Social Editor. He promises to tweet more at @riordanl

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Comment (2)


    Tuesday 7 July 2015

    Thanks for yet another clickbait headline.


      Tristan Rayner

      Tuesday 7 July 2015

      Clickbait: “content, especially that of a sensational or provocative nature”

      This is just explaining why you sneeze.

      Now if we said: ‘You Won’t Believe The Reason You Sneeze When You Click On The Sun It Changed Everything’ – I’d agree with you Dean.