[ELI5] what is the chemical/biological reaction that makes people sneeze when looking into the sun

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[ELI5] what is the chemical/biological reaction that makes people sneeze when looking into the sun

In: Chemistry

Why does this also affect some people only, like whenever I go out and I look into the sun or just there’s a really intense sun I feel the necessity to sneeze two or three times whereas this doesn’t seem to affect my parents nor my brother. (English not main language sorry for mistakes)

It’s called the greatest name ever:

Autosomal Compelling Helio-Ophthalmic Outburst (ACHOO) syndrome

https://en.wikipedia.org/wiki/Photic_sneeze_reflex

The tldr is they don’t really know, it’s nerve stuff, but it’s not 100 for sure why or what is crossed

And it’s hereditary! (Passed down to kids)

This phenomenon/condition is called Photic Sneeze Reflex and it’s believed to be genetic. It’s not well understood yet. I’m guessing it isn’t something that gets a lot of research resources.

The best theory I’ve heard is that some stimuli, usually exposure quickly to bright sunlight after being dark-adapted (used to being in a dark space for some time) causes a reflex reaction that is similar to an irritation in your nose. It may feel like it, or it may just be that the nerves trigger in the same path. That triggers a reflex of sneezes.

Think of it like getting goosebumps. The stimulus there could be cold, or fear, etc. Different things can stimulate the same reflex.

Be grateful it isn’t sunlight causing your knee jerk reflex I guess. HTH.

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Reflexive sneezing induced by light, and sunlight in particular, is estimated to occur in 18 to 35 percent of the population and is known as the photic sneeze reflex (PSR) or the ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome.