I think if the concentration of each of the ingredients is the same, then you can just measure out the amount that you need. I think they say "Don't use on cats." because probably someone, somewhere, at some point and time decided to use dog stuff on a cat and it probably made the cat very sick or it died as it overdosed the animal. There are natural ways to prevent fleas but I'm not sure what those ways are and how effective they are.
Last edited: