You can bring in flea eggs on your shoes or clothing and if your cats ingest them they turn into tape worms. We have a tick problem. Have to spray the yard every 10 days for 3 times to get eggs, larva and all. I hate them!!! One of my Pyrenees has just been scratching herself raw. She has scratched all the hair off her belly and left a nice soft warm pallet for ticks to latch on. The other Pyrenees still has thick belly hair and not many ticks. We have treated the yard, the dogs, between treatment sprays, 7-dust. It is getting better. I have her belly pretty much healed up now.