Bests & Worsts Reviews from Amazon

I'm very particular about my cats, they're my little girls and I love them. I use the Advantage product to keep them flea-free. I usually buy these from Amazon, but this last batch did not seem to be effective. Normally, when I apply the flea-treatment my cats react moments after I squeeze the medication on them. I can tell the treatment is affecting them adversely. They couldn't have cared less when I applied this batch though. There is usually a very distinct odor to the treatment, which this batch did not have. And they got fleas. Lots of them. I'll probably buy this through Amazon one more time just in case I got a defective package. If that is also ineffective, I'll have to pay more at my vet. I'm worried these are some kind of fakes in an effort to hit pricing goals.