We used this product on our cats for a long time and they still ended up getting fleas a lot. Our vet told us that these topical remedies don't work. If you really wsnt to peotect your cats get some anti flea collars. We get them every six months and since we got them we haven't had flees or ticks st all. And before, even when spraying oir cats from top to bottom im flea spray it wouldn't keep them away. Another advantage of getting a collar is that it's les traumatic for the cat. We spooked our cats a couple times beforr but not with the collars. And after two days the protextion is still active, but it's no longer harmfull to humans. So your cst csn still be pet even eith these collars on. I can't remember rxactly what brand we use but when I do I'll come back and tell you.