Pyrethrins are produced by several different species of the chrysanthemum plant and contain natural insecticides. The active compounds within the pyrethrins attack the nerve system of the insect, making it unable to fly. Because the effect is not always deadly, other ingredients are often added to help pyrethrins kill insects. Pyrethrins are used in pesticides for insects like fleas, ticks, head lice, mosquitoes, cockroaches and beetles.
Shampoos made to eradicate lice from a human's head often contain pyrethrins to help kill the parasites. Do not use these shampoos on children who are younger than 2 years old. Pyrethrin shampoo is typically applied two to three times with several days between each application to kill both the live lice and their eggs. Using lice shampoos containing pyrethrins could result in a red, itchy scalp or more serious side effects, like trouble breathing and large sores on the head. Contact your doctor if you experience these more serious side effects.
Flea and Tick Products
Pyrethrins are used in many different products for flea and tick prevention and eradication in dogs. For example, pyrethrins are present in many flea dusts, shampoos, spot-on treatments and flea collars. If you have a household with both dogs and cats, do not allow the pyrethrin-containing flea and tick product to come into contact with the cat. While pyrethrins are safe for use on dogs and can be very effective in controlling pests, they are toxic to cats and can result in sickness and even death.
Pyrethrins are safe enough for use on human skin and are therefore present in many bug sprays. The pyrethrins in bug spray will paralyze and possibly kill any bugs that land on you. Because pyrethrins are not a deterrent for bugs to come near you, most bugs sprays also contain oils and scents that are unappealing to bugs. Pyrethrins are included in both bug sprays intended for the skin and those for use around the house.
When your home becomes infested with roaches, fleas or mites, sometimes the best way to get rid of them is with a fogger. Place several fogger canisters throughout your home. Before activating them, cover counter tops, children's toys and other items that should stay clear of the fogger ingredients. Activate the fogger, leave your home and remove any pets for the amount of time indicated on the package. Many foggers contain pyrethrins because they compromise the central nervous systems of bugs.