This is a copy of another post of minethat you might never find:
We focus intently on graphic/gross things because part of the brain's fear system involves something called "attentiveness". It sounds mild but it's very important and a very strong instinct. Looking at it this way helps: if someone were pointing a gun at you, you would not see, hear or feel anything else around you. And you would probably stare at the gun, focussing intently with your eyes and frozen in that position. This is because the gun presents a life-threatening danger to you, and your brain tells you that you must "watch it" in case it makes a sudden move. Now this instinct is important when it comes to bears or rattlesnakes or whatnot, but with vomit or guns it seems kind of ridiculous. However, depending on the severity of the phobia, most phobics will find themselves frozen and staring at someone being sick, or vomit on the road or whatever (even staring at people who say they feel sick)- even though that seems counter-productive.
Thing is, it IS counter-productive. One way to begin healing is to FORCE YOURSELF to look away. Say to yourself (if you can) "what the hell am I staring at this for? It's not going to run toward me and kill me!"Then look away. The less you focus on the scary thing, the better.
I hope this helps a lot of people who had this same question for a long time (I know I did - and was fascinated at the answer).