I have used Sergeants flea and tick spray in the past and never had any problems. I had even used it on very young kittens. Just applied it right at the sink to kill most of the fleas off and then imediatley washed it off. BUT this past year using it in the same matter and even on kittens “OLD” enough to use product according to their label, I have had them all die left and right. I didnt realize it was the product doing this beings I had no trouble in the past but now I know that this product is a cat killer. I urge everyone to be very aware of this product as well as the Hertz. Ive never seen such horror in mylife when its came to my pets.