Plus, Achoo is more fun to say and literally makes perfect sense, too. Achoo syndrome is also lovingly called "sun sneezing" or sometimes the semi-technical nickname "photic sneeze reflex." ...
This is a phenomenon known as Photic Sneeze Reflex. Another name is Autosomal dominant Compelling Helio-Ophthalmic Outburst syndrome. Yep, that spells "ACHOO", and some call it "ACHOO Syndrome".
The sun can cause you to sneeze if you have a disorder known as ACHOO syndrome. Meterologist Ray Petelin details how the reaction is caused.