Check out the link below. It explains everything. Scientists aren't sure what causes this, but think the abrupt change in light triggers something in the optic nerve which in turn triggers the sneeze. You're not alone.
http://kidshealth.org/kid/talk/qa/sneeze.html
hi,im sure next time you sneeze,take a close look at the light rays from the sun and try to see the dust particles floating in the rays of light,im sure youll see the huge amounts of dust in the light,all you are is sensitive to dust and probably can smell carbon monoxide smells when no one else can,as i do,all you have to do is make sure you are driving slow when you feel a sneeze coming on because i had to practically pull over once from the extreme way i had to sneeze,i turned into the suns rays and puf,so it gets worse,to the point of getting chemically sensitive,so if you are not yet good,but im almost 40 years old and im using more organic products because im getting dizzy spells from chemical store products,so you are not nuts,they just dont study sneezing