I noticed that one of my 14 week old kittens was scrathing at his neck quite a bit. His brother hadn’t been scratching, but I decided that it would probably be best to treat them both early to get rid of any fleas they may have. The package the Hartz product came in indicated that the drops would be safe for cats over 12 weeks old and that it also killed flea eggs and their larvae. I assumed that the product would be safe for both kittens. I soon discovered I was wrong. I administered the flea drops to both kittens as directed. Shortly after I did so, I noticed they were both trying to lick their backs between their shoulders as if to remove the product. I became a bit concerned and wanted to make sure that ingesting the product wouldn’t be harmful to them. Since it was late at night, I decided to call the 24-hour emergency clinic/hospital to inquire about the product. Immediately after telling the veterinarian technician what I had put on the kittens and their ages, he put a veterinarian on the telephone. The vet explained that the product (Hartz OneSpot Flea Egg and Larvae Treatment) could be very harmful to my kitties. He instructed me to wash them off immediately with mild soap and warm water and to rinse their backs and any area the drops had gotten onto thoroughly. He also explained the symptoms that I needed to watch for over the next 24 hours. He said to make sure the kittens were not having a hard time walking or keeping their balance. He also told me to watch closely for any tremors, shaking or other odd behavior. The vet explained that the chemicals used in Hartz are too strong and often they have the same effect on cats/kittens as they do on fleas. He also told me that using FrontLine or Advantage brand flea medicines would not only be my safest, but also most effective bet. He explained the difference in the chemicals in such products and how they work so much more effectively. I was so thankful and proceeded to wash my kitties immediately. Please, if you are considering using a similar Hartz product, reconsider. It costs a bit less, but is most definitely not worth the risk. If you have already used this product, please wash your pets if possible and never ever use it again. I wish you the best of luck with your feline and K9 family members!