Is Sergeant's Silver Flea Spray for cats okay to use on ferrets?

It most likely would be ok if you used this on your ferret, however make sure the medications are not to strong. The best thing yo do would be to ask a sales associate at the pet store or your vet. I also know that when my kittens were young, they were under six months and no flea medicine was made for cats that age, we dipped them in dawn soap, and that handled the fleas very nicely. Hope something works!