Bright light can trigger sneezing in about one in four people. This odd reaction, called the photic sneeze reflex (PSR). We often see this phenomenon on sunny days or when someone steps out of a dark room into the light.

The exact reasons behind this reflex are still unknown. Some researchers think it could be related to the brain sending mixed signals.  These signals could mess with the body's nerves. It could be due to people having a super-sensitive parasympathetic nervous system.  It could be due to a scattered signalling from the nerves around the eyes.

  The exact details about what makes light cause a sneeze are still a bit fuzzy.  It is difficult to  reproduce this response in a lab setting. We need more information on how bright the light needs to be and what kind of light triggers it.

Trying to figure out what makes some people sneeze in the light is a bit like solving a puzzle. There are some studies out there that have tried to pinpoint the specifics.  They include four case reports and  three experiments.  But there are different ways to test this out and the answers are different therefore hard to compare.

There are no clear answers yet.  There are too many different ways to study this and no clear way to compare the results.  The answer to why light causes sneezing in some people is still unclear.  Future studies should aim to standardize their methods and really dive into the details of light intensity, color wavelength, and timing to understand more about this mysterious reflex.

Back in 2020, a search of MEDLINE, Google Scholar, Google Books,  and Google. Using  multiple languages to find information on this topic.  It turned up 167 records but only 7 were focused on testing light parameters.

Science and research needs consistent ways to test things.  Light and sneezing is no different.   To really understand PSR we need proper scientific research.  This will help us understand why and how it happens

Information is available but it is not consistent.  Researchers need to look at why some people sneeze and other people may not.  More systematic approaches are needed to fully understand this phenomenon.

Sneezing in the Sun: Why Bright Light Makes Some People Sneeze

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