Took Brandy to the vet and found out she has mites. We have used Revolution once a month since she was 8 weeks old. We heard that Advantage worked just as well and you didn't need a prescription, so tried it. Huge mistake. We live on a beach and Brandy loves to run and dig in the sand. We had been traveling for a few months so as soon as we got home, we let her play in the sand. Come to find out Advantage has nothing to control mites but Revolution does. Cost over $100 for the vet and treatment. Definitely back to Revolution.