Cyfluthrin is in a group of human-made insecticides called pyrethroids.¹ It was first registered in the US in 1987. It is used in agriculture to control insects that feed on cotton, turf, ornamentals, hops, cereal, corn, fruit, and potatoes. It can also be used in residential settings. Cyfluthrin is used to control pests like ants, silverfish, cockroaches, termites, weevils, fleas, mosquitoes and flies.²

Products containing cyfluthrin may be a solid, granule, powder, total release fogger, or liquid.³ There are over 150 products with cyfluthrin that are used in agriculture, inside homes, in the yard, and to protect wood from insects.^3,4,5 Some products may be used in agricultural aerial applications and as cattle ear tags.^3,4

Cyfluthrin acts as a stomach poison and through contact with the insect. By attacking the nerves, cyfluthrin causes constant muscle spasms. Eventually, the insect is paralyzed or starves.⁶ It is less toxic to people and mammals because they break it down faster than insects.⁷

If you are too close during an application of cyfluthrin at home or in public, you could get it on your skin, in your eyes, or breathe it in. Spills or other accidents could also cause exposure to cyfluthrin through the eyes and skin, or by inhaling or ingesting it.

You may be exposed to very low levels of cyfluthrin in your diet. Pesticides used on crops have tolerances, which are legal limits set by the US Environmental Protection Agency (EPA) to help ensure food safety.

When using pesticides, take precautionary steps to minimize your risk.

• Follow all label directions.
• If liquids are used indoors, open windows and turn on fans to speed up drying time.
• Stay away from the treated area (indoors, lawns, public places) until it has dried or settled, or for the time listed on the label, whichever is longest.
• Think about what items have been left outside. Cover or move toys, pet items, play structures, and grills.
• Cover edible plants before an outdoor application.

Cyfluthrin is poorly absorbed through the skin. Around 1% may be absorbed following a dermal exposure.³ If eaten, 80-90% of cyfluthrin is absorbed into the bloodstream.⁹ Cyfluthrin is rapidly distributed through the body.¹⁰

Cyfluthrin quickly leaves the body. More than half is excreted within 24 hours.¹³ Around 98% is eliminated from the body within 1-2 days.¹¹ Cyfluthrin is primarily eliminated in urine and feces.¹³ The highest concentrations of cyfluthrin found in the body were in fat. Smaller concentrations were found in the ovaries, liver, and spleen.^11,13,15

Small amounts of cyfluthrin have been found in milk after dairy cows were fed daily doses up to 28 days. Concentrations in fat tissues tended to be higher than the concentration in milk. It was also found in eggs when hens were fed cyfluthrin for three days.¹²

Cyfluthrin has been classified as "not likely to be carcinogenic to humans" by the EPA.¹⁶ A group from the World Health Organization evaluated many studies and found there was no link to cancer in rodents.¹¹ Rats and mice did not show evidence of cancer risk in long term feeding studies.³ It has not shown evidence of causing tumors or causing mutations to genes.^3,11

Dogs fed a moderate dose of cyfluthrin for three months had vomiting and incoordination. Dogs fed cyfluthrin for six months had tremors, loss of movement control, convulsions, and diarrhea.³ In another study with beagles, changes in body weights were seen. Females fed a high dose of cyfluthrin for 12 months showed a decrease in ovary weights.¹⁷

Rabbits showed no symptoms after cyfluthrin was applied to their skin for three weeks.⁹

The effects of cyfluthrin have been studied on pregnancy and development. Pregnant mice fed a low dose of cyfluthrin for at least 7 days had some young with weak bone formation of the skull, ribs, and fingers. The young mice also had changes in behavior compared to mice with mothers that were not fed cyfluthrin.¹⁸

Rabbits fed cyfluthrin showed no developmental effects.³ Cyfluthrin is low in reproductive toxicity and did not affect pregnancy rate or litter size.¹⁷ Pyrethroids (like cyfluthrin) have not been found to cross the placenta in substantial amounts or collect in the fetus.¹⁹

There is no evidence cyfluthrin disrupts endocrine function.²⁰

Children younger than age 6 are potentially more sensitive to pyrethroids than adults. Adult bodies may break down pyrethroids more quickly than children.³

Young children may also act in ways that put them at greater risk of being exposed. For example, they may spend more time near the floor or ground. They may also be more likely to place their hands in their mouths after touching treated surfaces. Consider taking precautions to reduce your child's risk of exposure.

Based on cyfluthrin’s chemical properties, it may have the potential to build up in animals. However, in laboratory studies with rats, cyfluthrin was quickly excreted from the body.^11,23

Bees are highly sensitive to contact with cyfluthrin.^6,23 Cyfluthrin is very highly toxic to fish and freshwater invertebrates like water fleas.^1,6 Cyfluthrin is low in toxicity to earthworms.^1,13

When eaten, cyfluthrin is slightly toxic to sheep and rabbits.¹³

Cyfluthrin is practically non-toxic to slightly toxic when eaten by birds, including ducks, quail, and hens.^2,6,23 It is moderately toxic to canaries.²