Science Questions

What causes the Photic Sneeze Response?

I was told that the reason we sneeze when looking at a bright light, is that the light causes our eyes to water, which drains into our noses via the tear ducts, which irritates the nose causing us to sneeze! James, Cambridge

Chris -   No.  People did think but it happens too quickly.  The photic sneeze reflex to recap is when you go out on a sunny day, bright light comes to you and you suddenly feel this irresistible urge to sneeze often multiple times.  About one person in five is affected, tends to run in families, and it seems to be a neurological phenomenon.  It’s not a tear tickling your nose phenomenon because you tend to sneeze quicker than your eyes water so people have sort of written off that theory unfortunately.  So we think it’s more the same thing that makes your pupil get smaller and you blink in response to bright light, probably the same bit of the brain that’s doing that is also crossing over into the sneezing center a little bit and triggering both reflexes.

Ben -   So it’s wiring rather than plumbing?

Chris -   Absolutely!

July 2009