photic sneeze reflex


I remember seeing years ago in one of your columns your statement that the photic sneeze reflex serves no purpose. Indeed it does! Remember that mother nature (okay, evolution) is a miser and anything that doesn’t serve an evolutionary purpose will be kicked to the curb. Here is the real reason for the photic sneeze reflex. I know this because I had a roommate in college who was able to keep his eyes open while sneezing. It is so simple I’m surprised that no one has told you about it by now. Okay, okay. I’ll get to the point. Your eyes have little drain tubes in the corners by the nose. They drain the tear drops away from your eyes and into the nasal cavity. It would be bad if fluids and germs could flow from your nose to your eyes when you were laying down, so the tubes have one-way valves much like the many other one-way valves in your veins, heart, etc. It’s a basic mechanism that your evolution has come up with. So the tear drops can flow down into the nose but nothing can flow back up. Good so far. Now comes the answer. The valves are very small and fragile. The force of a sneeze could easily break or damage them causing the potential for eye infections. So when you sneeze your body quickly forces the eyes closed, blocking the valves firmly behind much more tissue and muscle thereby protecting them. My roommate in college who was able to force his eyes opened when he sneezed ruptured the valves. They never repaired themselves and he was able to do party stunts by blowing air out of his eyeballs, actually out of the small tubes, providing us with endless amusement. Don’t try this at home as there is the real risk of chronic eye infections. By the way there is a current fad amoung eye doctors today to sew the valves closed for middle-aged, computer staring, contact wearing dry-eyed patients to lessen the tear drainage.

So you’ve proven there is a reason why we close our eyes when we sneeze. However, the photic sneeze reflex is different. That term refers to the tendency some people (myself included) have to sneeze when exposed to bright light, like when walking outside. Those people also close their eyes when they sneeze, however. Hope that clears up some confusion.

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Why do some people sneeze when going out into bright light?

If you hold your eyelids open while sneezing, will your eyes pop out?

Smeghead, it looks like our friend ajbiegen was using the term “photic sneeze reflex” that applies to the subject of the first article mentioned above, but may have been referring to a statement made by Cecil Adams in the second article, to wit