This is an article that I read tonight...

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The part I found interesting was:

A second possibility is that two nerves (the optic nerve and trigeminal nerve) are too close together in photic sneezers. Langer says light may cause stimulation of the optic nerve in the eye, which then coactivates the trigeminal nerve in the face, and results in an achoo reaction.

I've had the so-called ACHOO syndrome, or Autosomal Dominant Compelling Helio-Ophthalmic Outburst for as long as I can remember. It is a very common reaction. I caught it from my mother.