BE AWARE. Frontline has come out with a condensed? formula for the larger dogs. I have used the big dog dose on the ferrets for years and years (at one time we were taking in over 300 ferrets a year and they were coming in loaded, especially from animal controls) and have had no trouble. (HATE using it on the Danes as there is so much of it, it runs off onto the hairs before reaching the skin) Well now they have made it stronger/less in the vial (not sure if they put a # behind it or anything). Our vet did call them and they warned us against using it on the ferrets. I believe Advantage is the same. Another to check into is Adams. It has come out with the skin treatment - I have used their spray for years too on the ferrets and it has been marvelous, even the vets brag on it and it is across the counter. Just try to stick to the flea only not get in that Mosquito repellant and the other additives. No need to put stuff into their bloodstream they don't need. Millie Sanders, Director for the Texas Ferret Lovers Rescue with connected hospice and sanctuaries www.txferretrescue.org [Posted in FML 7807]