No they dont.I was there today its just 2 seconds. It just scratches a bit and hurts just after 4-5 hours. It just feels like a pinch for 2 seconds and then it is over it is nothing to worry about...
Because people relate blood to pain. Also because of nerves sending signals to the brain. A good way to stop it hurting is to freeze the area injected.....it works with me anyway....
Injections hurt because it is going into your skin where your muscle is and also the muscle has a slight reaction so when any little thing touches it hurts