It's mental, not physical. Most people don't throw up because they don't find it as revolting as you. If someone threw up, I just think,"Wow, someone's really sick." not "HOLY stuff CHUNKS OF CHEX AND OATMEAL EVERYWHERE IN BILE AND BLOOD." I'm pretty sure when you see someone throw up that it's so revolting to you that your body mimics what's happening, causing you to throw up.
For example, if someone screamed and saw a spider, the other person next to them would scream(assuming what they say was absolutely horrifying, and then reacting in the same way). If someone saw a spider and said,"Holy stuff" but not in a screaming tone, the other person would be likely to mimic and follow through with something like,"What the forget..."
You have to change the way you think about it.
Lols, one time someone threw up in my class, then another threw up, then another threw up. It was like family guy XD
