Both my girls a mini schnauzer and a mini schnauzer x mini poodle have had a dose each. One has semi sensitive skin and gets the odd mild reaction. They used to be on sentinal spectrum but recently ticks have become more common in my area so we used to use a spot on or collars aswell so I was looking forward to this new treatment amd the vet recommended it. They had the chews end of December and so far so good no reactions no ticks no fleas no side effects at all no change :) will continue to watch them but im pretty darn happy with it so far and I havent heard any thing bad talking to other owners in day to day life and work. So I keep my fingers and toes crossed for you all!