I know that sometimes when some people feel the need to sneeze they look at a light and this triggers a sneeze. I, too, find this helps. What doen't help, however, is when I walk out of somewhere dark or shaded into somewhere bright, whereupon I break into a violent sneezing fit. These fits usually contain around 5-7 sneezes although my record is 9. This causes great helarity amongst my friends and often to passers by. It has happened as long as I can remember and although it's never been a huge problem I just would like to know why.