The allethrins are a group of related synthetic compounds used in insecticides. They are synthetic pyrethroids, a synthetic form of a chemical found naturally in the chrysanthemum flower. They were first synthesized in the 1949. Allethrin was the first pyrethroid.The compounds have low toxicity for humans and birds, and are used in many household insecticides such as RAID as well as mosquito coils. It is highly toxic to fish and aquatic invertebrates. At normal application rates, allethrin is slightly toxic to bees. Insects subject to exposure become paralyzed (nervous system effect) before dying. Allethrins are toxic to cats because they either do not produce, or produce less of certain isoforms of glucuronosyltransferase, which serve in hepatic detoxifying metabolism pathways.They are also used as an ultra-low volume spray for outdoor mosquito control.