Photic Sneeze Reflex: Why Some People Sneeze At The Sun

I have at times been perplexed by the amount of sneezing I do at seemingly random intervals, deducing that I probably just have allergies to something.

During a meeting today, I needed to walk from one building to another. It was a gorgeous sunny day in Fremantle, and as we approached the second building, I couldn’t help but let out three muffled but aggressive sneezes.

“Sorry about that!” I said, embarrassed. “I think I must be allergic to one of the trees or something around here, it gets me all the time.”

The woman I was meeting with didn’t miss a beat before responding, “No, it’s probably the sun.”

Apparently, this is an actual thing.

The Photic Sneeze Reflex is a legitimate medical condition which causes people to sneeze when exposed to a variety of stimuli, including looking at bright lights.

Strangely, the earliest know record of the Photic Sneeze Reflex lives in the writings of Aristotle.

‘Why is it that one sneezes more after one has looked at the sun? Is it because the sun engenders heat and so causes movement, just as does tickling the nose with a feather? For both have the same effect; by setting up movement they cause heat and create breath more quickly from the moisture; and it is the escape of this breath which causes sneezing.’

Aristotle

Aristotle thought that the sun might cause nose sweat, which could tickle the inside of the nose enough to illicit a sneeze. While the logic checks out, this isn’t actually how it works.

Scientist’s best guess at the moment is that the sneeze reaction has something to do with the overstimulation of the trigeminal nerve,

Image result for trigeminal nerve
NHS

This nerve is the connection point for three other nerve branches including; the ophthalmic branch, which can be stimulated by rapid changes in light conditions; and the maxillary branch, which when stimulated, can cause sneezing.

The running theory is that when the opthalmic branch is overstimulated, it can cause other branches of the trigeminal nerve to become irritated.

A 2010 study discovered that if you’re amongst the 18-35% of people who report sneezing at the sun, you almost definitely have a very specific and seemingly pointless inheritable genetic mutation.

For those of us with the mutation, the irritation passed on to our maxillary nerve from overstimulation of the ophthalmic nerve through bright light changes is just enough to send us over the edge and into a small fit of sneezes.

The condition is harmless unless you’re a brain surgeon, but one hell of a nuisance nonetheless.

You can test whether you’re affected quite easily. Just walk outside and look at the sun for a while (not directly, obviously). If after thirty seconds or so you wind up achoo-ing your head off, welcome to the Photic Sneeze Reflex Club. You’ll receive your card in the mail.

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