Pyrethroids are man-made (synthetic) insecticides that are chemically similar to natural pyrethrins. Pyrethrins are produced by the flowers of the Chrysanthemum plants. There are currently more than twenty different kinds of pyrethroid chemicals.

Pyrethroid insecticides are found in many home-use and agricultural-use insecticides. Pyrethroid insecticides also are used for control of disease carrying insects such as mosquito abatement activities.

Pyrethroids are neurotoxins. They poison the nervous system by binding to certain kinds of proteins on nerve cell surfaces called sodium pumps. They block the ability of the sodium pumps to do their job - moving sodium from outside the cell to the inside of the cell. The exchange of sodium and calcium from inside the cell to outside the cell and back is how nerve cells transmit messages. Blocking the process stops the nerve cells from working, which results in paralysis for the insect.

Pyrethroids are an important public health tool for controlling insects that act as disease vectors (mosquitos, fleas, ticks, lice, etc.) and for controlling venomous insects (bees, wasps, etc.).

Some types of insects are able to develop resistance to pyrethroid toxicity.

Pyrethroids can be found in different kinds of household products such as insecticide aerosols (spray cans), shampoos for lice, and gardening pest management solutions.

List of some common pyrethroids

Allethrin Bifenthrin Cyfluthrin Cyhalothrin Cypermethrin
Cyphenothrin Deltamethrin Esfenvalerate Etofenprox Fenpropathrin
Fenvalerate Flucythrinate Flumethrin Imiprothrin λ-Cyhalothrin
Metofluthrin Permethrin Phenothrin Prallethrin Resmethrin
Silafluofen Sumithrin τ-Fluvalinate Tefluthrin Tetramethrin
Tralomethrin Transfluthrin      

Health concerns

Normally people are not as sensitive to pyrethroid toxicity as insects. The sodium pumps on human nerve cells are different than those on insect nerve cells and human livers are able to convert pyrethroids into non-neurotoxic metabolites. However, some metabolites may be toxic to other organ systems. A small percentage of people may experience allergic health effects from exposure to pyrethroids such as nausea, runny nose, skin rashes, eye irritation, and asthma like symptoms. Even fewer may experience mild neurologic effects, typically a burning or tingling sensation on skin (particularly skin had contact with pyrethroid containing insecticides), headaches, lightheadedness, dizziness, or a feeling of fatigue. These symptoms typically go away after cleaning exposed skin and a few hours of recovery. Very rarely, a person may experience more serious symptoms such as depression, increased salivation, excess sweating, muscle twitching, blurred vision, seizures, coma, and respiratory stress or failure.

Person's experiencing any health effects after using any insecticide should call the Poison Control Center (1-800-222-1222), or if the symptoms seem life threatening (i.e., difficulty breathing, changed mental state, or coma, etc.) call 911.

Pets and domestic animals, like people are not typically sensitive to pyrethroid exposure, but some individual animals may be. Sensitive animals will experience similar effects to those of sensitive people, and may need veterinary assistance to stop those symptoms.

Sources of additional information

Agency for Toxic Substances and Disease Registry (ATSDR)

U.S. Environmental Protection Agency (EPA)

National Pesticide Information Center

Last Update: April 25, 2016