the actual injection can feel weird. you can feel the liquid going in. It's like a hose, when you put your thumb over part of it and the water sprays out harder. It also feels like for a few seconds a pool under your skin, like the liquid may come back out the little hole. It won't but it feels that way. That feeling must freak him out. Don't know what you can do about it. Maybe give him a treat before and after?