Amazing! I kept an open mind when I read the other reviews about how effective this shampoo was, but I was massively impressed. Despite two rounds of flea drops my little collie mix was still scratching terribly and keeping us up at night with it. After just one wash there was a 90% improvement and I am very confident that another wash will completely smash it. If I could bow down to you over this message, I would. Worth every single penny and this shampoo will be a permanent fixture in my bathroom from now on!