I would never use OTC products on pets . ALSO some of the vet prescription flea/tick meds will kill your pet just as easily and more grossly . Advantage Top Spot is the one I used regularly once a mnth on my dog (& a few times on my cat + he now has some very small grey tumors on inside of ears )as she was flea/allergic so needed keep them off her, what I did not know til too late was that over a period of time this stuff causes tumors/cancer and anemia from that , at the end she had huge tumors in EVERY organ in her body , her belly was so swollen near the end it was tight to the touch , she bled-out when one of the tumors exploded inside of her ( she was in the vets care at the time & he was doing everything possible to help her ) so then I told him just put her down she's in too much misery & pain . After this all happened I researched ALL of these prescription meds for pets in depth on the web on the maker's sites , read until my eyes went crossed for weeks until I found one that is relatively safe compared to all the others , REVOLUTION is the BEST prescription flea/tick med out there in regards to Safety & long term use on both cat & dogs and it works great too . I only wish I had known all this before using the Advantage that the 1st vet had said was fine to use ( I trusted that he knew all about the RX meds).