^^^ YES, the store-bought flea shit is TERRIBLE. Don’t use the powder, don’t use the colors, don’t use any pills you can find at Target.
Get any and all flea, tick and worm treatments from a veterinarian. And even then, be discerning and skeptical and ask lots of questions. Be willing to spend more on the medication that the vet gives to his/her animals. If it’s a good vet, that is.
It’s not just cats either.
I’ve seen the cheap shit powder take strips of skin off of a short-haired American Staffordshire Terrier. Like acid. Purebreds have a lot of sensitivities and health issues of course, but that wasn’t the reason for the flaying. That shit is toxic by design, and it can seriously fuck animals up.
The dog I’m talking about was fine, by the way. Unlike my dog. Who is now dead.