Why do some of us sneeze when going from darkness to sunlight?



Why do some of us sneeze when going from darkness to sunlight?

In: Biology

A.C.H.O.O. Syndrome (yes,seriously) aka “photic sneeze reflex” isn’t fully understood but is thought to likely be caused by the fact that eye and nose nerves run into the brain in the same place so a very strong signal from the eyes might get misconstrued as a signal from the nose needing a sneeze to clear it.

I do this too. I read years ago only 25% of people do this. It doesn’t happen all the time for me but if I ever feel a sneeze coming on that isn’t “fully rendered” I can glance up at a light or the Sun to force it to finish. Pretty useful for me haha. Having a half way sneeze is a very annoying feeling.


My theory is that I squint a lot when it’s really sunny. Hence my nose is scrunching and irritating anything settled in there. Not to mention nose hairs raking around in there.

I don’t really notice the need to sneeze when wearing sunglasses. Only when I’m squinting with no sunglasses on a bright day.

[veratasium had a video explaining this](https://youtu.be/e69XZJ9DEj0)

I thought everyone did it until my wife was worried that our infant son had some allergies because he’d sneeze everytime we went outside. Turns out we’re in a minority

Some people sneeze when they see a pretty girl! https://en.wikipedia.org/wiki/Sexually_induced_sneezing