I don't have any dogs, but I have heard that a neem-based insecticide for pets is effective and safe.

Also, diatomaceous earth is supposed to be good for this. It, too, is safe for mammals.

And do not forget, during and after the natural delousing, to vacuum like crazy wherever the dog hangs out - chairs, etc. - and throw the bag away (if it is a paper bag.) Hope this helps!

Oh, most important: animals who are strong and clean on the inside of their bodies don't attract fleas. So I say, give them what is necessary to keep their blood clean and healthy, and the fleas will not be interested. It's like chickens and salmonella: if your chicken house is clean and dry, not overcrowded, and the chickens are fed a natural diet, and not overstressed, they just don't develop salmonella. (Speaking from my experience with my chickens.) They don't get any kind of filth-type disease. Anyway, there's all kinds of natural-medicine books for pet owners.