I'm usually prone to getting nervous and blushing whenever someone approaches me first and is the aggressor. UNLESS of course we're in a dimly lit room or outside in the dark (or right in direct bright sunlight so that it's so bright it's hard to see anything).
For me, what causes my blushing most often is the FEAR of blushing and others noticing it. If I know it would be difficult to "notice" a blush, it won't happen. Weird! Department stores, grocery stores, and office buildings are the worst- florescent lighting!! Over the years the excessive blushing has caused totally visible social anxiety like trembling hands, quivering voice, etc. It's really just an embarrassing day to day existence being me.
And really hot chicks will definately set off my "fight or flight" nerve responses: my heart beats really fast, I can't talk, and I can feel my face getting hot. This really sucks because I don't judge people by their looks and I treat everyone as equals- regardless of how they look, their race, or how intelligent they might be. My body reacts in complete opposition to the way my mind WANTS to react! Good looking women are no better as people than anyone else, I don't know why my mind tortures me like this. I want to be comfortable in front of everyone. Why is this so difficult for me?!?!?!?!?!?!?!?!