I have used the orange rind on my dog who had a significant problem with fleas. I rub the inside of a peel all over her and then rub it in. It makes her smell heavenly meanwhile but really does a number on the fleas. I also made a spray by boiling 7 or 8 rinds down and filtering it. It is unbelievable how well this works. This and vacuuming seemed to eliminate our flea problem.
Another natural remedy for fleas is orange rind. Very good for kittens and for your home. I don't know if it works on dogs. Orange rind contains natural chemicals (pyritherins I think) that kill insects. It must be fresh. Use an orange zester - the large or small gauge. Both will express the orange oil out of the skin. Then just move fresh zest over your cat's fur and watch the fleas fall dead. You do not have to rub it in- gentle moving it around in the vicinity of the cat works well. Cats really don't like the orange but it works so well and harms nothing. I zest oranges before making juice and then toss the zest on carpets, let it set about 10 minutes and then vacuum it up. For furniture I place muslin or a sheet on furniture to protect it. Flea free.
I am going to give the amethyst remedy a try too.