This simple product, in the past year, has proven itself 100%. There is a trick though. (You have to start using it BEFORE a flea infestation) This is a chemical-free preventative. It doesn't kill fleas, it makes your pet a less appetizing target. As a result, fleas won't want to hitch a ride into your home. Oh, and there is a bonus domino effect, my super-sensitive indoor cat has been scab-free for the first time in years!