I have never found any natural supplement that worked to repel fleas.
I have used Revolution for fleas and heartworm for years. I can say that I have never seen a flea on any of my dogs, never had a flea infestation in the house either. Revolution has worked for me wonderfully and I have 2 big dogs in the house. I have to use something WITHOUT Ivermectin in it, I have Collies and a lot of Collies cannot tolerate Ivermectin and it's not suggested to use anything with that in it.