My cats Storm and RB Pepper had fleas when I adopted them so they were treated with advantage for about 3 months. Then several years later Pepper began scratching and I found some large healthy fleas on him. I also found some smaller fleas on Storm and this was in Feb. They had to go to the vet and get advantage and also pills to prevent tapeworms which some fleas may carry. I've been using advantage every month on all of my cats ever since then and have had no problems since.

I live in a condo and other people in my building also have pets so if their pets aren't treated then the fleas will find their way to my pets. Good luck. Hopefully a one time treatment will do the trick.