I have an 8 year old persian who had fleas when we bought him at 10 weeks old. Because of his colour we didn't realize until he went to the vet for the first time how bad the infestation was. We have been battling ever since using Frontline (both the liquid on neck and spray which we bought in France where you can buy it without a prescription). We also have household spray, flea bombs and flea shampoo - all used regularly. NOTHING WORKED! We started to get bitten too and I was talking to the vet about another matter and mentioned how they were driving us crazy and she prescribed Advocate in conjunction with Indorex household spray. We used it on on both our cats (the other is a British Shorthair) and sprayed the house and it worked like magic. I would have recommended it to anyone without hesitation until I read some of the other posts which have shocked me. However, my cats had no side effects whatsoever and three weeks in we are flea free. I bathed my persian yesterday and his skin looks completely clear. For us it is brilliant.