Take a look at this. Great reviews, all natural, and was recommended to me by a brilliant member of The Cat Site who has never steered me wrong. My cats are all indoor, but they do go for occasional harness walks. I had been using food grade DE, which has worked just fine, but if your cat is indoor/outdoor, this spray may work well for you. I don’t apply chemicals to my cats, and I definitely wouldn’t to my diabetic boy. His system has enough to deal with. Hope this helps! https://www.homeoanimal.com/products/ticks-fleas-homeopathic-medicine