Natural Flea Remedies for Cats?

I have 2 cats, one who is allergic to fleas. I've read about natural treatments, but most disclaim they are unsafe or questionable for feline use. (Adding to the situation, bathing is pretty much a non-option as there is no hot water on tap at this time.) Any proven suggestions, info? Perhaps a 7thGen product I'm not aware of? Thank you.