Why do some people sneeze when looking at the sun?
Why does looking at the sun make me sneeze? Thanks for asking. We usually sneeze to protect ourselves from irritants such as pollen, dust or chemicals. But there are some people who consistently sneeze when they look at the sun. Achoo! In fact, it affects from 10 to 35% of us when we move from being in the shade to bright light, according to pbs.org.
If it happens to you, perhaps you've wondered if it was an allergy to sunlight, but actually it isn't. The reaction triggered by sudden exposure to light is called the photic sneeze reflex.
It's a congenital physiological anomaly that's pretty common and totally harmless.
Why does this reaction occur then?
When you're dazzled by bright light, the optic nerve sends a signal to the brain and you would normally blink or squint to better manage the sudden influx of light. However, the optic nerve is very close to another cranial nerve called the trigeminal nerve. The trigeminal nerve has a number of functions, like triggering the production of tears and saliva.
It also has a role to play when you sneeze because it's responsible for tissue sensitivity and has nerve endings around the nose.
It's thought that the optic and trigeminal nerves in some people are closer to each other, and it's as if they interfere with each other like two touching electrical wires. That's why those people sneeze when looking at the sun. What happens in the body when we sneeze?
A sneeze comes out through the mouth and nose because our nasal cavities aren't wide enough to withstand the pressure of the expelled air.
The trigeminal nerve tells the brain to inhale air, and the abdominal and intercostal muscles to contract, expelling dust, pollen, or in this case simply air, at speeds of up to 100 mph. According to a 2012 American study, which was updated in 2015 and published in Medical Genetics Summaries, there can be a hereditary aspect to the photic sneeze reflex.
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