I guess I have a fairly big aversion to needles. Not that I mind physical pain in general - I once fell off my bike while riding to school and didn't mind at all, just got up as soon as I physically could straighten my scraped knee and got back on the bike.

The thing is, though, that in fourth and fifth grade I was taking a medicine that required I be given a blood test every other week. I was not a happy camper. My mother usually held my hand while I started screaming, often at the touch of the alcohol, even before the needle went in.
I still remember hiding in the closet under the white coats one time while the lab technician tried to pull me out.
Not to mention that, one time, my doctor ordered the wrong test, so I had to come back 2 days later.
It once took a lab tech 4 attempts to find my vein. You can imagine my mood.

I am thin now, but at the time, I weighed so little that it was hard for me to run or do anything active for the rest of the day after the blood (usually 2 vials) was drawn.

Even now at the age of 18, I feel queasy when I go past the building where those tests were done, no matter how little reason there is for such a feeling. It's just planted too deep.