Sun Sneezing

By Anupum Pant

I was in the bus today. Considering the hot desert sun outside, it was fairly dark inside. The moment I stepped out,  sneezed. For once again it felt like there was something about the sun that made me sneeze. Instantly I was reminded of the countless times this has happened to me in the past. I asked a couple of friends and I found that most shared a similar experience. I had to find out more about it.

Turns out, about third of the people in our planet have their brains wired in a way that makes them sneeze when they see the sun – or more specifically, when a sudden change in light intensity occurs. It’s called photic sneeze reflex, photoptarmosis or simply “sun sneezing”. It’s one of those phenomena which are not totally understood till now, but there’s a good explanation for it.

It’s been noted for a long time. Even Aristotle had documented it in The Book of Problems. According to him it was the nose getting heated by the sun which caused it. However, his explanation for it wasn’t very accurate.

An English philosopher Francis Bacon proved his theory wrong by closing his eyes and letting his nose heat in the sun. He didn’t sneeze. His theory was that the sun made eyes water and the moisture in in turn irritated the nose, which causes you to sneeze. Not really.

This is how scientists explain it – As we all know, an irritation in the nose causes sneezing. That is because a nerve called trigeminal nerve senses irritation and sends a signal to the brain. This nerve is very close to the optic nerve. So, when the eye is exposed to sunlight, the optic nerve sends an electric signal to the brain. This signal, scientists think, leaks into the trigeminal nerve too and makes it fire a signal (saying “irritation”). And then you sneeze.

As it is understood presently, this is a genetic trait that is passed on to the offspring with a 50% chance of the offspring showing the same trait. So, if one parent sneezes in the sun, one out of two of his kids will have the same reflex.

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