Flea dirt continuing once fleas are dead?

Hello! Last week I noticied a lot of flea dirt on my cats and in the house. I went to the pet store and purchased topical Sentry brand flea control and applied it to each cat. A few days later I noticed that one of the cats still had visable flea issues. We bathed him in dish soap and fould and killed about 10 fleas. Since that time we have not seen fleas on any cats, but continue to see a lot of the flea dirt around the house.  We combed through the cats with a flea comb and pulled out a lot of dirt, but no fleas. Is it possible that the fleas are gone but the flea dirt remains?

Most over the counter flea meds are not good for killing fleas and they're not good for your cat.  I'd definitely seek the advice of a vet and get flea meds from him/her.
 

Flea dirt is actually flea feces, so no, there is still a flea problem. You may need to treat carpet and upholstery as well as obtaining better flea treatments to stop this problem.

Is home blitz a good thing to do before front line or after? Plz help