If there was no original sin, would I still sneeze?
We have to make some assumptions here, as the Bible doesn’t say a whole heaping lot about the day-to-day corporeal effects of Original Sin.
Taking a completely literal view of Genesis 3, we could probably quite confidently say that before the fall, everything was ‘perfect’, but that’s not a terribly rigorous term (for example; if Adam & eve needed to eat, did they require the assistance of intestinal bacteria? did they excrete and if so, were there such things as harmful fecal bacteria?).
Anyway, we could conveniently say that disease wouldn’t be around, so you wouldn’t need to sneeze because you caught a cold, because there wouldn’t be any colds to catch. But I can’t see why there wouldn’t be such things as feathers and thistledown (although of course the thistles themselves would not be prickly) - and if you shoved something fluffy up your nose, you’d need to clear it somehow.
It’s really and impossible question to properly answer because there are far too many problems with the idea of taking Genesis completely literally - once you start to interrogate the concept of absolute physical perfection (in the context of terrestrial life), it’s hard (or maybe impossible) to find an explanation that doesn’t make complete nonsense of biological and physical systems.
On the other hand, without it, YOU wouldn’t be around, so don’t complain. 
Um… why?
Probably because confusion over Augustine’s term “concupiscence” makes people think Original Sin had to do with sex.
BZOOOOO (…I hope I spelled that right!..): what makes you ask the original question?
The devil made him do it!
Not necessarily. I know orignal sin doesn’t have to do with sex, but I also note there was no mention of reproduction or sex until after (directly after) The Fall (first thing they did actually :)) so I might conclude there was no need for it beforehand.
But if we’re talking about Augustine, he believed we had complete control over our bodies before the fall so involuntary spasms like sneezing or orgasms would be out of the question.
And since he invented it, I guess he’d know :).
But then you’d be able to sneeze voluntarily, wouldn’t you?..