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Common name: PERMETHRIN

Type: pesticide
Chemical class: synthetic pyrethroid


Molecular structure of PERMETHRIN






Type of action: Broad spectrum contact, non systemic ectoparasiticide: insecticide, acaricide, tickicide, louisicide, larvicide
Main veterinary parasites controlled: flies, ticks, mites, lice, fleas, mosquitoes, etc.

Efficacy against a specific parasite depends on the delivery form and on the dose administered. 

Click here for general information on features and characteristics of PARASITICIDES.


Dosing recommendations for antiparasitics depend on national regulations. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasiteCheck the labels of the products available in your country for specific information on approved indications.

The table below indicates some usual dosing recommendations for permethrin issued by manufacturers or documented in the scientific literature. They may not be approved in some countries.

Dosing and efficacy of permethrin products depends a lot on its cis:trans isomeric composition (e.g. 25:75, 40:60, 80:20). The higher the cis-isomer content the higher the efficacy at the same dose, or the lower the dose required to achieve the same control than with the low-cis product. Unfortunately many manufacturers do not indicate the cis:trans composition in the product labels, which may create confusion.

As all synthetic pyrethroids, permethrin products are always used for topical administration, either as concentrates for dipping or spraying, or in ready-to-use products such as pour-ons, dressingsear-tags for livestock and spot-ons or low-cost topicals for pets such as shampoos, soaps, sprays, etc. Permethrin is used massively in pets worldwide, with hundreds of different brands. Use in livestock is lower because cypermethrin is often preferred in many countries. 

Permethrin (and many other synthetic pyrethroids) acts by contact (i.e. it is not systemic) and is effective against most external livestock and pet parasites (flies, ticks, mites, lice, fleas, mosquitoes, etc.) but is completely ineffective against internal parasites.

However, resistance to all synthetic pyrethroids is already very frequent worldwide and can be extremely high, particularly in cattle ticks, horn & buffalo flies, houseflies, red fowl mites, mosquitoes, fleas, etc.

Dosing recommendations for PERMETHRIN
Delivery Parasites Dose (against permethrin-susceptible parasites)
Bath Fleas, ticks, lice, mites, etc. 100-250 ppm (= mg/ml) in the wash, dep. on isomers & indications
Spot-on Fleas, ticks, lice, mites, etc. 30-200 mg/kg. High intolerance risk in some breeds
CATS. Pyrethroids are mostly toxic to cats!
Delivery Parasites Dose (against permethrin-susceptible parasites)
Dip, spray Ticksflies, mites, lice, etc. 50-400 ppm (=mg/ml) in the wash dep. on isomers & indications
Pour-on Ticksflies, mites, lice, etc. 2-10 mg/kg, dep. on isomers & indications
Delivery Parasites  Dose (against permethrin-susceptible parasites)
Dip, spray Ticksflies, lice, mites, etc. 50-400 ppm (=mg/ml) in the wash dep. on isomers & indications
Pour-on Ticksflies, lice, mites, etc. 2-15 mg/kg, dep. on isomers & indications
Delivery Parasites  Dose (against permethrin-susceptible parasites)
Spray Lice, mites 50-400 ppm (=mg/ml) in the wash dep. on isomers & indications
Pour-on Lice, mites 2-8 mg/kg, dep. on isomers & indications
Delivery Parasites  Dose (against permethrin-susceptible parasites)
Spray Ticks, flies, lice, mites, etc. 50-400 ppm (=mg/ml) in the wash dep. on isomers & indications
Pour-on Ticks, flies, lice, mites, etc. 2-10 mg/kg, dep. on isomers & indications
Delivery Parasites  Dose (against permethrin-susceptible parasites)
Spray Ticksmites, lice, etc. 100-200 ppm (=mg/ml) in the wash dep. on isomers & indications

DISCLAIMER: Liability is denied for any possible damage or harm to persons, animals or any other goods that could follow the transmission or use of the information, data or recommendations in this site by any site visitor or third parties.


Oral LD50, rat, acute*:  430-4000 mg/kg depending on vehicle and content of various isomers
Dermal LD50, rat, acute*: >4000 mg/kg
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.

WARNING: Permethrin is toxic for cats!

Synthetic pyrethroids can be irritant for the skin and the eyes.

MRL (maximum residue limit) set for animal tissues (either beef, mutton pork or chicken)*:

  • CODEX: Yes
  • EU: Yes
  • USA: Yes
  • AUS: Yes

* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock. MRL's for animal tissues may be set also for agricultural pesticides that are not approved for use on animals but are used on commodities fed to animals. A MRL may be also set in the form of an IMPORT TOLERANCE for active ingredients not approved in a particular country but approved for imported animal commodities.

Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.

Learn more about permethrin safety.

General information on the safety of veterinary antiparasitics is available in specific articles in this site (click to visit):


Never use agricultural or hygiene products with this or any other active ingredient on livestock or pets, even if there are veterinary products with this same active ingredient approved for use on animals. The formulations for agricultural or hygiene use are different and may be toxic for livestock or pets.

It is obvious that veterinary products are not intended for and should never be used on humans!!!


Decade of introduction: 1970
Introduced by: FMC, ICI, SHELL, SUMITOMO, etc.
Some original brands: ECTIBAN, STOMOXIN
Patent: Expired (particular formulations may be still patent-protected)

Use on LIVESTOCK: Yes, moderate.
Use on HORSES. Yes, abundant.
Use on
DOGS: Yes, massive.
Main delivery forms: 

Use in human medicine: Yes
Use in
public/domestic hygiene: Yes
Use in
agriculture: Yes
Generics available: 
Yes, numberless



On livestock: Yes, as for all synthetic pyrethroids: very frequent worldwide in such species as cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), houseflies (Musca domestica), mosquitoes.
On pets: Yes, quite frequent worldwide in dog and cat fleas (Ctenocephalides spp).

Learn more about parasite resistance and how it develops.


Permethrin is a synthetic pyrethroid with a spectrum of activity similar to cypermethrin. It is vastly used on dogs, substantially less on livestock. It is also vastly used in agriculture as well as in public and domestic hygiene. Together with cypermethrin it is one of the synthetic pyrethroids most used worldwide.

There are also many mixtures: with amitraz, organophosphates, carbamates, insect development inhibitors, etc. Many products contain also synergists.

Permethrin used in veterinary products can be of different "qualities" regarding the content of various optic isomers (cis or trans) that show different efficacy against parasites. You can learn more about such mixtures of optic isomers in the article on synthetic pyrethroids. For most users, it often doesn't make any difference regarding efficacy, because if one product uses a mixture with more of the most effective isomers, it will be used at a lower concentration than a product using a mixture with less effective isomers. However, some isomers are significantly more toxic than other ones, and this can negatively influence the tolerance of livestock or pets to a particular product.

Efficacy of permethrin

Permethrin is an ectoparasiticide, i.e. active only against external parasites such as flies, ticks, mites, lice, fleas, mosquitoes, etc. It can be considered as a broad-spectrum generalist, i.e. quite good against almost all insects, ticks and mites, but not outstanding against a particular parasite. It is certainly less efficient against multi-host ticks (e.g. Amblyomma, Rhipicephalus, Ixodes, Dermacentor, etc.) than several other tickicides (e.g. amitraz, chlorfenvinphos, coumaphos, flumethrin, etc.).

As most synthetic pyrethroids, permethrin is a mediocre larvicide, i.e. it is often not a good option for the large-scale prevention of cutaneous myiases (e.g. screwworms, blowfly strike, etc.) with sprays, pour-ons, etc. However permethrin is often included in dressings for the therapeutic treatment on animal injuries already infected with maggots.

Permethrin, as well as many other synthetic pyrethroids has a significant repellent effect on certain insects and ticks, which strongly depends on the delivery form and the dose administered.

However, resistance to permethrin is widespread and can be very high in cattle ticks (Boophilus spp), horn flies (Haematobia irritans), red poultry mites (Dermanyssus gallinae), sheep lice (Damalinia ovis), houseflies (Musca domestica), dog and cat fleas (Ctenocephalides spp) and mosquitoes.. As a consequence, products with permethrin are already totally useless against these important parasites in many places. The same applies to all other synthetic pyrethroids (e.g. cypermethrin, deltamethrin, flumethrin, etc.). And this is true for whatever delivery form: dipping, spraying, pour-ons, ear-tags, shampoos, soaps, etc.

Pharmacokinetics of permethrin

Topically administered permethrin remains mostly on the hair-coat of the treated animals and is very poorly absorbed through the skin. In contrast with natural pyrethrins and older synthetic pyrethroids permethrin is quite resistant to UV-light, which allows a residual effect between 5 and 10 days for most sprays and dips.

Treated animals can ingest permethrin through licking or grooming. Absorption to blood is low. The absorbed permethrin is quickly metabolized in the liver to non-toxic metabolites that are excreted through urine. This is done by a specific enzyme called glucuronidase. However, cats lack this enzyme and cannot metabolize permethrin and other synthetic pyrethroids. This is why permethrin and most other synthetic pyrethroids are toxic to cats.

As a general rule permethrin products are approved for use on dairy animals and on laying hens in many countries.

Mechanism of action of permethrin

Synthetic pyrethroids, including permethrin, have a similar mode of action as organochlorines. They act on the membrane of nerve cells blocking the closure of the ion gates of the sodium channel during re-polarization. This strongly disrupts the transmission of nervous impulses. At low concentrations insects suffer from hyperactivity. At high concentrations they are paralyzed and die.

Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.

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