best way to treat fleas?

okay i have tried   diatomaceous earth and it has not worked, the fleas are really bothering the cats and i dont know what else to do. can anybody tell me some safe flea medicine for my cats? or if there is anything else out there that will help?     

I use Queen City Animals nitenpyram, which is the same thing in Capstar, only a lot less expensive, to kill fleas.  To prevent infestation, I use the same brand Lufenuron (same stuff in Program), which sterilizes fleas so they can't reproduce.  It is given once a month; the other is as needed, and safe as often as once a day if necessary.  It has worked for me and I haven't seen the side effects I've seen with other flea meds.

okay  thank you. i will have to give it a try 

Previously I used frontline and flea shampoo, but I've read the you can use apple cider vinegar either spray them with it or mix it in with a shampoo so I might try this next time.

Although I don't know what the forum's stance on it since I'm new, because it seems it can mess up the pH balance of a cat if they ingest it.

We use Advantage or Activyl. I prefer these as they do not get into the bloodstream (Revolution and Comfortis do...though I have heard good things about the Comfortis.)

CapStar works to kill adult fleas within 30 mins (usually quicker.)

You could give CapStar in the morning and then put a topical on that afternoon.