Why do I Sneeze in the Sun?
Photic sneeze reflex - when the exposure of the retina to bright light after an extended period in a darker environment induces a sneeze (Everett, 1964). This phenomenon was defined by Dr. Henry Everett in 1964, however it was reported as early as 1954 by an ophthalmologist who noticed patients would sneeze when he used his ophthalmoscope’s light to look into their eye (Everett, 1964). There have been many interconnected mechanisms proposed as to why the photic sneeze reflex occurs (Langer, Beeli & Jäncke, 2010). One compelling hypothesis is that people who have this reflex have a more sensitive and excitable visual cortex and overstimulation by a bright light causes a reflexive nose tickling sensation (Langer, Beeli & Jäncke, 2010). The same study also suggests that people with the reflex anticipate the stimulus more and thus become even more sensitive to its effects (Langer, Beeli & Jäncke, 2010). A report from 1995 states that this reflex occurs most often in Caucasian females (Semes, Amos & Waterbor, 1995). It is also most common to sneeze 3 times or less and all within 19 seconds (Semes, Amos & Waterbor, 1995). The origin of this reflex is most likely genetic; pedigrees show that an autosomal dominant gene is the most likely mode of inheritance (Forrester, 1985). So, next time you can't stop sneezing in the sun, thank your parents!
This sneeze reflex could prove to be an important factor in surgery particularly during the COVID-19 pandemic. During eye surgery, regional anesthesia is applied near the same nerve that is stimulated by the photic sneeze reflex, the trigeminal nerve. Involuntarily sneezing during a surgery could cause healthcare providers to be exposed to disease transmitted via aerosolized droplets. In order to maximize beneficence and non-malfeasance to both the patient and provider, a new mechanism for anesthesia has been proposed that targets a different nerve. They have also suggested using another object to block any possible droplets from transmitting called an aerosol box.
Everett, H. C. (1964). Sneezing in response to light. Neurology, 14(5), 483-483.
Forrester, J. M. (1985). Sneezing on exposure to bright light as an inherited response. Human heredity, 35(2), 113-114.
Jaichandran, V. V., & Raman, R. (2020). Aerosol prevention box for regional anaesthesia for eye surgery in COVID times. Eye, 1-2.
Langer, N., Beeli, G., & Jäncke, L. (2010). When the sun prickles your nose: an EEG study identifying neural bases of photic sneezing. PloS one, 5(2), e9208.
Semes, L. P., Amos, J. F., & Waterbor, J. W. (1995). The photic sneeze response: a descriptive report of a clinic population. Journal of the American Optometric Association, 66(6), 372.
This is such an interesting topic. I myself am an example of someone who almost always sneezes after coming out of a dark room. Since this is thought to attributed to a more sensitive and excitable visual cortex, it would be interesting to see if individuals who have synesthesia have this occurrence as well. Synesthesia is a condition where individuals have one sensory stimulation that triggers another. Most people are familiar with grapheme-color synesthesia, where someone associates letters or numbers with colors. This is thought to be caused by an overactive visual cortex. With that being said, it would be really interesting to see if these individuals with grapheme-color synesthesia, or synesthesia in general, are more sensitive to the photic sneeze reflex.
ReplyDeleteHubbard EM, Ramachandran VS. Neurocognitive mechanisms of synesthesia. Neuron. 2005 Nov 3;48(3):509-20. doi: 10.1016/j.neuron.2005.10.012. PMID: 16269367.
I have always wondered why people have suggested looking up at the overhead lights in order to assist the sneezing process, now it all makes sense. I also find it interesting how this photic reflex happens in such a small population of people. One study found that only 25% of the sampled British population had the photic sneeze reflex. This is likely due to inheritance as you had mentioned it is an autosomal dominant gene.
ReplyDeleteForrester, J. M. (1985). Sneezing on exposure to bright light as an inherited response. Human Heredity, 35(2), 113–114.