Happens for blood draws as well, even small quantities. Happens if someone pokes me with a lidocaine. It's a vasovagal reaction where my body "overreacts to certain triggers". My blood pressure and heartrate plummet (to scary low levels. I've freaked out nurses on a couple of occasions). It causes me to feint in a comically dramatic way because the bloodflow to my brain gets too low. To be even more fun, I sometimes exhibit false "seizure" symptoms when I'm down, tightening up all my muscles at once and stopping breathing. During my first COVID vaccine, my breathing stopped for almost a minute, which is why 2 doctors were overseeing me when I came to. My wife explaining the situation is the only reason I didn't end up in an ambulance. You shoulda seen the nurse, she looked as pale as I did!
In theory, this could kill me, and there are confirmed ultra-rare cases of people dying from vasovagal syncope. In practice, I'm far more likely to die of a car accident on the way home (with my wife driving me because I'm in no state to drive after that). So long as a competent medical professional is watching me, I'm basically completely safe. But absolutely miserable.
Honestly, it makes me feel like I'm some kind of drama queen. But it's entirely made up of unconscious responses in my body.
And the weird thing is that it's not thinking about needles. It's my body's reaction to the feeling of a needle entering it. That sad little "prick" feeling that is maybe a 1 out of 10 on the pain scale? I have no idea if it's "trickable" because I have absolutely no problem digging out a splinter with a knife. I keep wanting to find out if getting a tattoo would trigger that reaction or not. I just want to get a tattoo anyway lol.