Originally Posted by Birdgunner
Pyrethrin is a relatively safe insecticide for pets and one of the most common AI's found in flea treatments, even if a dog or cat ingests some it typically breaks down in their stomach acid and causes no ill effect, poisoning can happen but it is very rare... Permethrin, the synthetic version of Pyrethrin however is a different story and not as kind to cats.
You have basically just stated the equivalent that Arsenic will not kill people because it is in the food we eat (and it is).
Sorry, man. Pyrethrin can be deadly to any pet in a relatively small dose (though not always of course) - it's all about application. Why do you think you are instructed to apply flea preventative to the back of the neck - so they cannot lick it off. All they have to do is walk on freshly treated yard area, lick their paws and they can go toxic. Do you have any experience with treating Pyrethretic animals??? If not you should stick to commenting on experience instead of what you pull from the quick Google search. If so then speak to that experience with an example. Pyrethrin is NOT pet ingestion safe at all and should be avoided. The only thing you got right is that Permethrin is even more toxic.
My wife (emergency vet) treats Pyrethrin toxicity fairly often and it is usually not fatal with treatment. Much of the time it is overdose because a cat/feline is given canine flea preventative. Dog prev is not only a larger dose, but a stronger dose, so cutting back a dog dose for a cat requires looking at the dosage strength, not just the size - most homeowners fail to recognize this and thus they toxify their cat. She has also seen cases of toxicity due to yard spraying.
BTW - The synthetic derivative, Permethrin, should never be used on cats in any circumstance.
It baffles me that people spread misinformation of such important topics without any real knowledge (or giving any experiential examples).