I breed Scottish Fold cats & have 3 inside, we never had a problem with fleas until we fostered a few kittens for the local animal shelter, I tried the powders & remedies you get at stores like Wal-mart to no avail, so I bought Frontline Plus from my vet. While we did see a slight relief from the fleas on the cats they all 3 had huge scabs where we applied the oil & they were in obvious pain. I checked with my vet & we had used the correct dosage, he informed us that almost 50% of his "patients" have had this reaction. I found Revolution online with excellent reviews & so we tried it with marvelous results! Revolution protects against fleas, round worm, heart worm, & ear mites, it works immediately & our cats love it!