These plants grow naturally in the Middle East, Europe, Japan, and most importantly, Kenya. Pyrethrins affect the nervous system of insects and result in repeated and extended firings of the nerves. They do this by affecting the flow of sodium out of nerve cells. Pyrethrins are used to control ticks, fleas, lice, Cheyletiella mites and mosquitos. They are mainly found in products applied directly on the pet.
Synergists are chemicals that enhance the performance of other drugs.
The synergist most widely used with pyrethrins is piperonyl butoxide. All pyrethrins are easily hydrolyzed and degraded by stomach acids so toxicity following ingestion by pets is very low. Toxicities, although rare, do occur. A cat or dog with pyrethrin toxicosis generally will salivate, tremor, vomit and may seizure. Generally signs of toxicosis will be gone after 24 hours.