I can't keep my eyes open when I sneeze and nor can anyone else I've asked. Why? Someone told me that if you don't close your eyes your eyeballs will fly out under the pressure caused by the sneeze, but it sounds a bit unlikely to me.
Sneezing is a complex reflex action involving muscles of your face, throat and chest. As it is a reflex action you have no control over your eyes closing. If you could keep them open I don't think they would fly out - but a sneeze is pretty violent with the sneeze coming out at over 100 mph, so it your probably makes sense for your body to force them closed.
When I sneeze, it certainly doesn't feel like there is a lot of pressure on my eyelids. The eye-closing reaction might be to keep the sneeze out of the eyes, or it might have no purpose at all (the toenail question jumps to mind).
Popular web 'fact'; When you sneeze, all bodily functions stop ... even your heart! Well what about the dreaded fartsneeze then? that function don't stop.. so, untrue?
xyzzy, that reaction is because when your body is in shock you lose control of certain bodily functions. That is why, in motoring accidents, for example, many people lose control of their bladder and / or bowels as many an ambulance crew member can testify to.
I've heard its because your eyes would actually fall out if they didn't close. Don't quote me on that though, whether this is true or not I'm not sure...