A sneeze seems like the simplest reflex your body has. But the science behind it gets weird fast. Here are three sneezing facts that sound made up, and every single one of them is true.
1. Why bright light makes some people sneeze
It has an official name, and it's a pun. Scientists call it ACHOO syndrome, short for Autosomal Dominant Compelling Helio-Ophthalmic Outburst. A group of geneticists came up with the acronym while chatting at a conference.
It's far from rare. Estimates range from about 18% to 35% of people, and it runs in families. It usually strikes when someone steps out of the dark into bright light, like leaving a movie theater on a sunny afternoon or driving out of a tunnel.
Nobody has fully explained it. One leading theory is that light hitting the optic nerve also sets off the trigeminal nerve, which handles sensation in the face, so the brain reads it as an irritation in the nose. People have wondered about it for ages: Aristotle puzzled over sun sneezing around 350 BC.
2. Why you should never hold a sneeze in
Pinching your nose and clamping your mouth shut can do real damage. In a case published in BMJ Case Reports, a man in his 30s tore a hole in his windpipe doing exactly that while driving.
He'd been dealing with hay fever when the sneeze hit. Bottling it up sent the pressure in his airway to more than 20 times normal, leaving a tear about 2 millimeters wide and air trapped in the tissue of his neck. Doctors believe it was the first known case of its kind. Luckily, it healed on its own within five weeks.
He isn't the only one. Holding in sneezes has been linked to fractured ribs, ruptured eardrums and even burst blood vessels in the brain. In 2018, another man in England ruptured his throat stifling a sneeze and had to be fed through a tube while it healed.
3. The sneezes that have nothing to do with allergies
For some people, the trigger is sex. Doctors have documented people who sneeze when they have sexual thoughts, and others who sneeze after orgasm.
It started when an ear, nose and throat specialist in England met a patient who sneezed every time he had a sexual thought. He didn't believe it at first, then searched internet chat rooms and found many more people describing the same thing. His paper ran in the Journal of the Royal Society of Medicine in 2008.
Once the story spread, more people came forward. The researchers soon counted 146 people who said sexual thoughts made them sneeze, including seven doctors. Their best explanation is crossed wiring in the autonomic nervous system, the part of the body that runs reflexes we can't control. And sex isn't the only odd trigger: some people with ACHOO syndrome sneeze when they pluck their eyebrows.
