Do you always sneeze when you go outside on a sunny day? You may be wondering why this happens. According to Scientific American, this is called the “photic sneeze reflex.” Many surveys have been done asking people if they sneeze when they are in the sun, and between 10%-35% said they do.
Aristotle believed that the heat of the sun on a persons nose would irritate it, causing it to sneeze. Bacon, an English philosopher 2000 years after Aristotle’s time, disagreed with his idea, claiming that he did not sneeze if his eyes were closed in the sun. Bacon then believed that the sun caused peoples eyes to water, which then seeped into the nose, causing the person to sneeze.
Nowadays, experts believe that people have this reflex due to “crossed wires in the brain.” According to Karen Schrock, a writer for Scientific American, “a sneeze is usually triggered by an irritation in the nose, which is sensed by the trigeminal nerve, a cranial nerve responsible for facial sensation and motor control.” The brain then sends a signal to the eyes, which is supposed to constrict the pupils. It is believed that some of the signal is sensed by the nose, tricking the brain into feeling irritation in the nose. An article on scienceline states that these reflexes are called the pupillary light reflex and the trigeminal reflex. The pupillary light reflex obviously controls the pupils, while the trigeminal reflex controls the nose, mouth, chest, and all muscles that are used while sneezing.
According to a video on the Huffington Post, if one parents has the gene, then there is a 50% their children will have the photic sneeze reflex. I know that this could be true, because my mom has very sensitive eyes and also sneezes when exposed to sunlight, and I also have the photic sneeze reflex.
Also, another theory is that people with this reflex have a more sensitive visual system in the brain, than people who don’t have the reflex, which causes them to sneeze.There is another hypothesis as well. The medulla oblongata, which is “a part of the brain stem that helps regulate many involuntary processes, including breathing, heart rate and sneezing,” (scienceline) mixes up the signals that are flowing to the brain, since they are all going to the same place.
This question got me thinking, and I wonder if it is just the sun that causes people to sneeze, or is it all bright lights? I know from personal experience that bright lights do not make me sneeze, just the sun does. I believe that it has to be very bright and strong light to make people sneeze, so a normal light would not make someone sneeze.
Overall, it is believed that the “wire-crossing theory” is the correct theory. The photic sneeze reflex is not harmful to people, and does nothing to our health. The only way to really prevent the sneeze would be to wear sunglasses when you go outside.