My 2 inside cats have never had fleas. They are 5 years old. Somehow this year they got fleas. I went to Petsmart and Banfield is located inside the store. I asked them about flea control. They recommended their First Shield brand as being as good as Frontline. I bought it. When asked, they said reactions if any would be within the first hour. They assured me they had received no complaints after selling this product over the last year or so.
My male cat had the reactions: within 30 mins, racing thru the house, (a coworker had forewarned me that their dogs do this so I wasn't too concerned.) 12 hrs later -- diahrea,and vomiting, 24 hrs later foaming at the mouth--that scared me a lot! An online vet said to bathe him really well to get the stuff off. I've done that now and will watch him closely overnight.
I only hope that there's no permanent damage as the online vet said First Shield is extremely dangerous and should never be used. They recommended Front Line only as being safe. I'm going to ask for my money back from Banfield -- guess we'll see how they stand. How irresponsible for a company to distribute something that's supposed to be safe for our pets and ends up harming them. That's just not right.