I placed a Seargants Gold flea collar for cats on my 12 year old cat Lucky. Lucky is used to wearing flea collars and has never had an issue. Within 2 hours my cat was stumbling, coughing, wheezing and crying in pain. His heart was absolutely racing. An hour or so after I scrubbed his neck area down, his heart rate finally returned to normal. I am happy that I was still at home to see this reaction, and had enough time to save him. I am saddened that I did not read reviews of this product before I tried it. It is disgusting that this company is still selling this product after all of these poor animals and pet owners have suffered.