Dear Matthew Alice: You know that horrible feeling when you need to sneeze but can't? If you look at a light just at that difficult moment the sneeze comes. Why? — Ron King, El Paso, TX
Congratulations, Ron. You're one of the genetically select who can conjure up what’s called in the trade a photic response sneeze. Actually, about the only sure bet here is the name of the phenomenon. Beyond that, science is in the dark, as it were. The reflex does seem to be a genetic trait — you either got it or you ain’t — but exactly what “it” is is still a mystery. Once again we’re reduced to best guesses. Nasal and optic nerves lie close to one another, so it’s not illogical to assume that any crossed wires might provide some cross-stimulation. When you’re stuck on the frustrating edge of a sneeze, looking at a bright light could make your optic nerves buzz, which in turn might tweak your nasal nerves just enough to provoke a satisfying sneeze. It’s one of those explanations that is reasonable enough to make the questioner go away satisfied without requiring any really deep thinking or grant applications. Definitely my kind of answer.