Have you ever walked outside during the height of allergy season and nearly sneezed your head off with a rapid-fire series of "Achoos"? If you're like most, the answer is yes, and while these sneezing fits are both annoying and embarrassing at times, there's a scientific reason for why you sometimes have to sneeze in quick succession. First, what the heck causes a sneeze in the first place, and what happens inside your body when one sneaks up on you? Well, sneezing is caused by a number of things, from dust and illness, to emotional responses and even sunlight, though...