I have nine cats and had been using another flea and tick medication for them until my son bought a whole year’s supply of Hartz on e-bay. After I received the medication, I started to hear the horror stories about this product. Even my vet said that Hartz caused violent reactions in cats plus it didn’t work. I contacted Hartz and they mentioned that in some instances people had problems. Since I had the medication, I decided to try it. I’ve had worse reactions with other medications than this one. Only one of my cats had a problem and that was some itching where the medication was applied. No fleas, no ticks, no dead kitties. This medication is working excellently. I live in a very rural area where we have extreemly heavy tick and flea infestation. Considering I have nine cats of varing ages from six months to 13 years old, I would have thought that if there were serious problems with this medication at least one of the animals would have experienced it?