However, it is known that accidental oral or dermal
exposure to high doses of pyrethrins can cause a
temporary numbness of the tongue and lips. Pyrethrum
extract has low acute toxicity to mammals and
birds despite a very high toxicity to insects, other
invertebrates and fish (lethal concentrations of a few
parts per billion in water). Tests with laboratory
mammals indicate that pyrethrum, even at high
doses or combined with piperonyl butoxide, does not
produce carcinogenic, mutagenic or teratogenic effects.
Any pathological changes observed at high
doses are in the liver.