Permethrin poisoning in cats

Information for cat owners




Permethrin poisoning is one of the most commonly reported poisonings in cats worldwide.

Permethrin is a commonly used insecticide that is safe around most animals, but cats are much more sensitive to this chemical than other animals. Concentrated permethrin-containing spot-on products are widely available from shops in many countries for control of fleas on dogs. Unfortunately it is these products that are often responsible for poisoning of cats when they are accidentally used on cats, or even when cats come into close contact with recently treated dogs.

Signs of permethrin poisoning can be life-threatening and include severe muscle tremors and uncontrolled seizures. Up to 40% of affected cats may die or need to be euthanased – prompt diagnosis and veterinary treatment are important to alleviate suffering and improve the chances of survival.

Better labelling of permethrin-containing products and better controls over their sale would do much to reduce the high numbers of cases of poisoning that are seen in cats.

What is permethrin?

Permethrin is a type of insecticide (insect killer). Permethrin is classified as a pyrethroid – these are a group of synthetic compounds derived from pyrethrins, which are naturally occurring substances extracted from Chrysanthemum flowers.

Permethrin and other pyrethroids act as neurotoxins – they exert their effect by binding to and blocking sodium channels on the surface of nerve cells, which interferes with nerve function. Because insects are much more susceptible to the effects of pyrethroids than mammals, these chemicals are widely used as insecticides, and are sometimes used for control of fleas and ticks on animals.

While permethrin has a wide safety margin for most mammals, meaning it is generally very safe to use, cats are highly sensitive to permethrin and are much more likely to develop signs of toxicity than dogs. Permethrin is fat-soluble and can be absorbed into the body across the skin, or after being swallowed. It is metabolised (broken down by) the liver and it is thought that cats have different liver metabolic pathways to other species (in particular a relative deficiency of the enzyme hepatic glucuronosyltransferase) leading to a poor ability to break down permethrin. This makes cats much more susceptible to being poisoned.

Cats are most commonly poisoned when they are exposed to the high concentration of permethrin typically found in some spot-on products designed to control fleas and ticks on dogs (see below).

Signs of permethrin toxicity

Exposure to even small quantities of concentrated permethrin can cause severe and fatal poisoning in cats. After exposure to permethrin, signs of toxicity usually develop within a few hours, but in some cases can take one to three days to become apparent. Common clinical signs of toxicity include:

  • Muscle tremors
  • Twitching
  • Seizures (as shown in the accompanying video clip)
  • Salivation
  • Incoordination
  • Fever
  • Dilated pupils

Unfortunately many cases of permethrin toxicity result in death of the cat, and from recorded cases anywhere between 10% and 40% of poisoned cats may die or need to be euthanased because of the severity of the poisoning. See permethrin poisoning cases.

A Ragdoll cat which luckily survived to tell the tale. The cat suffered seizures and tremors after a permethrin spot-on treatment designed for dogs was applied to its skin. After three days of intensive treatment and 48 hours’ sedation the cat was discharged with no complications.

How do cats become poisoned with permethrin?

Cats are usually poisoned by permethrin following exposure to the concentrated permethrin spot-on products designed to control fleas and ticks on dogs.

Many different flea spot-on products and shampoos/rinses that are manufactured for use on dogs contain permethrin. These products are safe to use on dogs, but not on cats.

Unfortunately, concentrated permethrin-based flea spot-on products are often inexpensive and widely available. Problems usually occur when owners buy products from shops where nobody is available to explain their safe use. Although the outer packaging of these products often contain warnings not to use them on cats, these may be missed. Often, owners do not realise that the products can cause fatal toxicity to cats. A dog product may be accidentally used on a cat, or sometimes owners mistakenly think that a product so widely available would not cause severe problems and may treat a cat with a small amount of the dog product, often with fatal results.

Another important way cats can become poisoned is when a dog in a house is treated with a permethrin-based spot-on and a cat then sleeps next to the dog, cuddles up to the dog or grooms the dog. This can lead to enough permethrin being absorbed by the cat to cause severe poisoning. It is recommended that cats are kept away from dogs for at least 72 hours after a concentrated permethrin spot-on has been used on a dog.

Although many products contain permethrin (including some fly sprays, ant powders etc.) it is usually only the flea spot-on preparations that contain high concentrations of permethrin and are therefore likely to cause significant toxicity to cats.

How common is permethrin poisoning?

Permethrin spot-on products are widely available around the world. There are now many reports of permethrin poisoning involving large numbers of cats from many different countries (including Europe, USA and Australia). Permethrin is one of the most common causes of poisoning of cats in many countries, with many thousands of cats affected. However, the frequency with which this occurs will depend on the availability of concentrated permethrin-based products, the regulations surrounding their availability, and the labelling used (clear warnings on permethrin products will reduce the number of poisonings through accidental use).

Diagnosis of permethrin poisoning

Diagnosis of permethrin toxicity is usually made on the basis of typical clinical signs, and known or suspected exposure to a permethrin-containing insecticide.

Treatment of permethrin poisoning

If you suspect your cat may have been poisoned, it is critical that you contact your vet as quickly as possible and get urgent treatment. Treatment of permethrin poisoning is largely supportive, as there is no antidote for the poison, but early treatment is important to avoid suffering. In general terms treatment involves:

  • Decontamination – Because most cats are exposed after having permethrin products applied to their skin, decontamination involves thorough washing of the cat with lukewarm water and a mild detergent. The aim is to remove as much of the product as possible to stop further absorption through the skin.
  • Seizure/tremor control – Treatment of muscle tremors may involve the use of methocarbamol (a muscle relaxant) or benzodiazepines (diazepam or midazolam) although the latter may not be very effective. Treatment of seizures may involve the use of drugs such as barbiturates (phenobarbitone) and sometimes even general anaesthesia or heavy sedation is required (propofol or alfaxalone).
  • General supportive care – Supportive care involves intravenous fluids, temperature monitoring and other nursing care. Cats may require several days of treatment in the veterinary clinic before slowly recovering.
  • Lipid infusions – Recently, some cats with permethrin poisoning have been treated with special intravenous lipid infusions. This appears to be helpful in some severe cases of poisoning (the lipid may help to remove the permethrin from tissues and reduce its toxicity).


Although the majority of cats with permethrin poisoning survive, this depends on the severity of the poisoning and in reported cases between 10% and 40% may die or need to be euthanased due to the severity of the signs, or the development of complications.

What can be done to prevent toxicity?

  • Banning the sale of concentrated permethrin-containing flea products: if general sale of these products from shops was banned (and they were only available from pharmacies or veterinary clinics, where appropriate advice could be given) this would dramatically reduce the frequency of permethrin poisoning in cats. However, such restrictions may not be possible as they would require a major reclassification of the products in many countries.
  • Increased regulation of concentrated permethrin products: While banning the sale of these products in shops may be difficult, a relatively simple reclassification of the products might mean that they could not be sold without advice being given by a suitably qualified person at the point of sale. This would be a huge step forward as the shop would then need to ensure that owners are adequately warned about the potential for poisoning of cats and confusion could be avoided. In the UK the ‘Pets at Home’ chain of pet stores is already putting a voluntary scheme in place to do just that.
  • Better warnings on packaging: Clearer labelling of concentrated permethrin-containing flea products, with prominent warnings on both outer packaging and individual pipettes (because they are often removed from the packet for storage at home) explaining that they are toxic to cats (and that treated dogs should be kept away from cats) is important to reduce misuse.
  • Better labelling: It can be difficult to tell what the active ingredient is in many flea products sold in shops. Clearer labels and packaging that showed the contents of the product prominently would help – there are many other very effective flea products (such as fipronil and imidacloprid) that are commonly available in shops and are safe for use in both dogs and cats (and may be more effective than permethrin as well). In addition, separation of dog and cat flea products on product display shelving in shops may help.
  • Public awareness: Owners are always encouraged to read product information (whether purchased from a shop, pharmacy or vet) carefully, and heed any warnings. If you have any concerns about any medication, always contact your vet for advice.
  • Notifying manufacturers and authorities: Whenever permethrin poisoning is known or suspected, it is important to notify both the manufacturer of the product and the local drug regulatory authorities (your vet can help you with this). Unless cases of poisoning are reported through these official channels, the scale of the problem cannot be determined.

What is International Cat Care doing to help?

International Cat Care has been actively involved in educating pet owners, members of the cat community and vets about feline permethrin toxicity, through conferences, letters and publications. We have also been campaigning to make the reporting of adverse events easier and for restrictions on the sale of permethrin products. We have also been campaigning for much clearer labelling and warnings to be added to all packaging of permethrin-containing flea products, and it is encouraging to see that this has been having some effect.

We have been active in discussing this problem with vets and veterinary organisations in many countries to help highlight the scale of the problem, and spread information about this important issue.

What can you do to help?

Help spread the word by letting your friends and colleagues know about this problem, and importantly, sign our petition for better regulation of concentrated permethrin-based flea products. Please encourage others to sign it too!

Be sure to always read product labels carefully, and if you are ever in doubt, contact your vet for advice.