When my son's cat Fu came to stay with me, he had fleas! I used a flea comb, dunking it in hot soapy water whenever I got a flea. After a few days of short, 15 minutes or so, treatments in the bathroom, Fu was flea-free! No chemicals! Fortunately only one other of my indoor kitties caught fleas from Fu but she had only a few and the same treatment worked with her too.
I use Frontline on the dogs but ONLY because they go outside to the dog parks - the kitties are all indoor. Bonnie