There are a good many myths about sneezing, for a common reflex that is.  In fact only one common myth that had been partially proven is that looking at a bright light will cause you to sneeze.  For about 30% of the population, looking at a bright light does cause them to sneeze.  Though no one is sure, some say that looking at a bright light triggers a nerve involved in sneezing by hitting a point in the retina, pupil, or even just squinting.  And don't worry; sneezing because of bright lights has a handy name.  It's photic-sneezing and it's not at all harmful.

            But still, many myths still remain untrue.  Such as the one about not being able to open your eyes when you sneeze.  It is possible if you try hard enough but I for one dont really care whether or not my eyes are open when I sneeze.  Another is that your heart stops when you sneeze.  That doesn't even have the possibility of being true.  Sneezing has to do with your lungs and muscles in your face.  I suppose if you sneezed long enough and couldn't get a breath your heart would stop beating because you'd have suffocated and died but you know, that's never happened.

            Another myth is more of what I would call superstition (I know they're like the same thing but if you think of myth you think more untrue reason and superstition is untrue response to action).  Have you ever said; bless you, after someone sneezes?  Most of the time it's just common courtesy but one superstition is that if you don't say it after you sneeze, the devil will jump down your throat.  But more common is a possible origin of saying 'Bless you' which was during the Black Plague where, if you got sick, it really was 'God Bless You.'  However sneezes most of time are preventing disease and infection rather than the signal that it has started (with exceptions like colds).