Back when my grandchildren stayed with me some 15 to 17 years ago I had two indoor female cats. Well using the drops on the neck the larger of the two just lay at the end of my bed for quite sometime, unable to eat and real lethargic. The smaller one was skiddish and scared of most people anyway (besides me), but she was a rescue from the street. I kind of overlooked her hiding so much as she did it often. Now all these years later I have a beautiful white male with blue eyes (which change 3 other colors depending on his mood), he is also deaf. The drops and the Ultra Guard collar (twice) make his pupils dilate and he acts scared to death of me. He is the biggest baby I have ever had, wanting his front paws rubbed continually and on top of me always. The deaf cats will do this for security but he was held and babied from the beginning. I am scared to ever try them again and will start using the mint oil after he is bathed. I just thought I should look it up since this is the 2nd time the collar has done this to his neurological system. Never again as my cats are my family!!