I put the flea drops of Hartz Ultra Guard drops on my cats’s neck in an effort to save money from the stuff I have been buying from the vet- “Advantage”. The ad in the paper that caught my eye sort of said to wise up and stop paying high prices. Well, I noticed he was licking his back neck area and then was not his peppy self. So I went online and saw your comments and got alarmed and washed it off with shampoo right away. I am throwing the rest of it out- here’s the thing I think; Advantage and the other high price stuff from the vets is not so much liquid on the neck. It was a lot of liquid in the Hartz tube and so my cat could reach to where it had soaked. It says to use all the liquid drops. I will pay the high price from now on- it’s worth it.