/looking at something gross/seeing someone else be sick?

it seems to me a very strange phenomena but is apparently quite common.
a woman on come dine with me did it last week after hearing someone talk about eating scorpions and alligator. (which doesn't even sound disgusting!) i cant quite get my head around having such a physical reaction just from listening to someone talk though! actually there re a few people that make me feel sick just by talking...but i digress.

has this ever happened to you?
know anyone that does it?

were you that wimp that was allowed to be excused from watching certain videos in science lessons on account of the scary blood?