Pyrethrins are widely used for control of various insect pests. There are two types that differ in chemical structure and symptoms of exposure. Both type I and II pyrethroids inhibit the nervous system of insects. This occurs at the sodium ion channels in the nerve cell membrane. Nerve cell membranes have a specific electrical charge.
Neurotransmitters help nerve cells communicate.
Electrical messages sent between nerve cells allow them to generate a response, like a movement in an animal or insect. Even though pyrethrins and pyrethroids are nerve poisons, they are not cholinesterase inhibitors like organophosphate or carbamate insecticides. Synergists work by restricting an enzyme that insects use to detoxify the pyrethrins. There are many different types of pyrethroids, but the remainder of this fact sheet will deal with pyrethrins. Information on specific pyrethroids is available in other fact sheets.