I have been on C for three years with no significant problems. I started out following their rotation guide then gradually started my own. I do not do my arms. There just isn't' much area to rotate there...I do have small indentations on my arms so I quit that area...I like to go sleeveless when it is hot. My stomach gets the inj's the most...lots of fat there and also my inner thighs. Make sure it is at room temperature. It takes a while to learn the needle setting for your different spots. If the needle is too short and doesn't go in to the fat...it can really sting. Yeah, I still get some red bumps or itchy spots but I just have to deal with that. Good luck to you!