No fleas on the dogs, yet, but I found one in my head. It must have been from the cat, because he sits on the top of my recliner, right near my head. I also give them Sentinel, but the vet said if it is a bad season, they really need both. And I have to give it to all of them at the same time to avoid the fleas spreading (2 dogs/3 cats). It's expensive, but worth not having fleas. We don't have a tick problem here, thank goodness.