I’ve not used any Hartz products since about 17-18 years ago when I learned a very, very sad lesson…
In the late 80s, I took in a litter (about 8) of kittens that had been abandoned by (sorry to say) someone I knew. They were absolutely infested with fleas. I bought the Hartz Flea and Tick Powder, read the instructions, which indicated that the kittens were well within the age of safe application.
Within a day or two, I found one of the kittens dead after I arrived home from work.
Another day or so later, another of the kittens began to convulse and was clearly in pain. We took this kitten to the vet, where, upon telling him the history of these kittens and his examination, he told me that they were poisoned from the Hartz powder!!! That kitten did not survive.
We immediately washed the remaining kittens, but, unfortunately only two did survive.
I wrote to Hartz at that time, but they never responded. This company has been marketing deadly stuff for our animals for a long, long time. Amazing that they can get away with this.