This was a few years ago, we had been using flea shampoos and decided to try the drops. We went to the store and bought some Hartz drops not knowing all the dangers, to put on our 2lb chihuahua and my 2 large cat about 6lb-15lbs and my kitten who was about 15 weeks old, I bought the smallest dosages for each, and only put about a half tube on my cats and like 2 drops on my chihuahua. Almost instantly my chihuahua started to show signs so we washed it off her, she was shaking, foaming at the mouth her eyes were rolled back in her head, we washed it off her and she seemed to be ok after about 20 mins, I also washed my cats to make sure they wouldn’t get sick, well it wasnt soon enough. My 6lb cat started seizing and foaming twitching, was so scary to watch her as she was healthy and happy jut 20 mins ago, then my larger cat got really bad he was foaming, twitching, almost lifeless not breathing regularly, I bought the smallest cat dosage and split 1 tube between them. I was terrified, my cat layed in a box 3 days unable to get up and walk he messed all over himself. I thought he was dead I raised these 2 form the time they were 2 days old, and here he was at 2 almost dead because of flea drops. He managed to pull through, but he was never right after that, he had some neurological issues from it. My other cat an kitten were ok after we got them washed and the foaming stopped, but my poo chihuahua lost all of her hair, she looked pitiful with no fur and all the scabs, I wish this site was out before i bought this, I will never ever use Hartz or Sergeants again not even their shampoos!