The Achoo Syndrome
A patient recently came up with an eye question I’ve heard many times over the years.
J.G. asked, “Doc, almost every time I drive through the tunnel from Monterey and I pop out into the sunshine, I sneeze! Why do I do that?”
Sneezing in the sunlight is a unique phenomenon. Not everyone experiences it and we don’t really understand how or why it happens.
Her friend, J.G. went on to say, was one day listening to this story and the prediction of an imminent sneeze and had serious doubts. But, sure enough, emerging into the sun J.G. promptly sneezed. Her friend was sure she was faking it! J.G. was not faking it, although you can pretend to sneeze. I once had a golden retriever, Ginger, who would immediately sneeze right after I did. It was a game to her, so I’d fake one two three more sneezes and she’d repeat all three with a thumping tail!
Those in the know have tried to explain why this happens for centuries.
Aristotle asked, “Why does the heat of the sun provoke sneezing?” Then much later Francis Bacon dismissed the whole notion when he faced the sun with eyes closed and he did not sneeze. He falsely concluded it was all boloney! Actually, we now know only about 25% of the population have this ability. Sir Bacon was unknowingly in that 75%.
I use the word ‘ability’ loosely; as though it’s a skill or a trait with a certain purpose. But there does not seem to be any value in doing this, nor is there anything negative, except for annoying those around you. Since the ACHOO syndrome, or ‘photic sneeze reflex’, as it’s been called, is not of dire medical import to understand, there have not been any large studies on this. But it is interesting nonetheless.
It’s an anatomical thing. Here’s how it probably happens: When the little hairs lining your nasal cavities are stimulated or bothered by something (wind, dust, pet hair, chemicals, allergies or the cold virus) they send a message to your brain to do something FAST to get rid of it. That message travels along the naso-ciliary nerve. Your brain reads the message and sends back the response to sneeze. And you sneeze. The cool thing here is that that naso-ciliary nerve does double duty and also picks up “stimulation” messages from the ciliary portion-your eyes. A sudden flash of light is not only ‘seen’ by your optic nerve. How your pupils react to light or any ‘electrical-type’ stimulus can also be picked up by that ciliary nerve. As that light message travels along to the brain, there’s a branch that signals the ‘naso’ (nose) part sometimes and you sneeze!
We now know that the ‘ACHOO syndrome’ is inherited in an autosomally dominant fashion. That means only one parent needs to be a ‘sun-sneezer’ to pass it on to half of his/her kids. And this trait affects men and women equally.
The sun is not the only culprit either. I’ve heard people say that they sneeze when they look into a campfire, or when the sun shines into their eyes off of a car’s metal bumper, (I’m dating myself as there are no more metal bumpers!) or even as I’m examining their eyes with my intense light instruments. It’s normal. I wonder. Do any of you have interesting examples of this phenomenon? Let me know.