I don't know why I was remembering this, but it sure is funny now....
I was one of those kids they would have to lay down to draw blood so they wouldn't faint. I remember once in college (before nursing school) I toured a animal behavior lab for a bio class I had and there were rats with these implanted IV catheters, and I almost fainted. When I first started to learn how to do shots --- on an ORANGE, no less --- I would get tunnel vision and my ears would ring!
I guess repeatedly facing your fears as a treatment for phobias really does work...I'm living proof.