Our Other Sites

Permethrin poisoning

30th July 2018

Permethrin poisoning

Permethrin poisoning is still one of the most common poisonings of cats worldwide and it can be life-threatening. Even worse is the fact that loving owners can accidentally poison their cats by using dog flea spot-on products containing permethrin because they do not recognise the dangers.

What is permethrin?

Permethrin is a pyrethroid, a synthetic pyrethrin. Pyrethrins are naturally occurring insecticides extracted from the flowers of Chrysanthemum cinerariaefolium. Permethrin is used in some flea spot-on products made for dogs, and occasionally (in lower doses) in flea powders and collars for cats. Unfortunately, exposure to concentrated permethrin (as in some dog spot-ons) can result in serious illness and even death in cats.

Why is permethrin toxic to cats but not dogs?

We often use the phrase ‘cats are not small dogs’ and this is certainly true when it comes to the way cats break down certain chemicals and drugs in their bodies.  The cat liver lacks certain proteins (enzymes) that break down some chemicals into harmless forms, meaning that the chemical can accumulate in the cat’s body and cause serious illness. This difference in drug metabolism is why we must never assume that a drug or product which is safe for dogs will be safe to use for cats.

How are cats poisoned by permethrin?

The most common way cats are poisoned is when owners use a dog flea product on their cat in error. They perhaps assume that the dog product is simply a higher volume of the chemical and that if they apply a small amount to the cat, that will be fine. Unfortunately, this is not the case and cats can become very unwell even after tiny doses of permethrin.

The other way cats are exposed to permethrin is by coming into contact with a dog which has recently been treated with a spot-on containing permethrin. The permethrin will stay on the dog’s skin and coat for some time and when a cat grooms or even rubs against the dog, or simply sits on the same furniture, it can be poisoned.

Permethrin-impregnated clothing: No cases of permethrin poisoning in cats after exposure to permethrin-impregnated clothing have been reported. This is unlikely to be a problem because of the low concentration of permethrin used and the low rate of transfer from the fabric. Most cases of poisoning in cats have been associated with the use of spot-on products which contain much higher doses of permethrin. Based on the available evidence the risk of toxicity from sleeping on or near a permethrin-impregnated shirt, for example, should be minimal, but if there is a specific concern it is always best to contact the manufacturer of the product.

What signs do affected cats show after contact with permethrin?

The signs of permethrin toxicity are very unpleasant. The chemical affects the cat’s nervous system causing tremors/shaking, twitching, oversensitivity to touch and sound, walking as though drunk and, in severe cases, seizures or fits. Less commonly, cats may have trouble breathing and may even become blind.

How are affected cats treated?

If you think you may have applied a flea product containing permethrin you need to contact your vet IMMEDIATELY. The same applies if you think your cat has been in contact with a treated dog.

The vet will initially try and prevent the cats from absorbing more permethrin through its skin by washing the cat with dilute washing up liquid. Further treatment depends on how badly affected the cat is, but medication often needs to be given to stop the tremors or fits. Cats often have to remain in the veterinary clinic for several days. In very severe cases the cat has to be given an anaesthetic to stop the fits and a tube put into its throat to help it breathe. A relatively new treatment (called lipid infusion) is available which helps to ‘mop up’ the permethrin from the cat’s system and may offer a better chance of survival for severely affected cats.

What is the prognosis for cats with permethrin poisoning?

Thankfully the majority of cats, if treated promptly by their vet, will make a full recovery. More severely affected cats, especially those suffering from fits that are hard to control, have a poorer prognosis and sadly may die or are put to sleep.

How can we prevent cats suffering from permethrin poisoning?

Permethrin poisoning is a very distressing condition and completely preventable.

  • Make sure you buy flea treatment solely designed for cats – it can be easy to pick up the wrong pack when dog and cat treatments are displayed side by side in shops
  • Be very careful if shopping online.  Many product descriptions do not include the active ingredients and any warnings may not be noticed in the small picture
  • Always read the instructions carefully and take note of any warnings
  • Never use a dog product on a cat
  • If you have dogs and cats in your home, choose a treatment for the dog which does not contain permethrin
  • If dogs are treated with flea products containing permethrin then they should be kept away from cats for 72 hours.
  • If you have any concerns about any medication, always contact your vet for advice.

Help to maintain awareness of the problem

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.


Case study – Jasper

Jasper,  a 5-year-old male cat, lives with his owner in Australia. As a caring owner concerned about flea control in her animals, Jasper’s well-meaning owner split a permethrin-containing flea spot-on product, manufactured for use on large dogs, between Jasper, their small dog and their pet rabbit.

Six hours later Jasper was found unable to stand, drooling and was shaking severely. Jasper’s owners contacted their local veterinary hospital – they had no idea what had caused the problems. The veterinary nurse on duty was able to advise them that immediate veterinary attention was required and brief questioning determined that this was a possible case of permethrin toxicity. The nurse advised the owners to bring the flea product packaging into the hospital for confirmation. The nurse alerted the veterinarian on duty and commenced preparing equipment ready for Jasper’s arrival.

When Jasper arrived he had severe tremors/shaking, was drooling, and was sensitive to sound and touch. There were greasy patches of fur where the flea product had been applied. Careful handling was required to be able to place a tube (catheter) into Jasper’s vein and he was given immediate treatment to stop his tremors. The regions of his fur where the dog spot-on had been applied were clipped and he was washed with a mild dishwashing detergent.

Initially, Jasper’s tremors reduced in severity.  However, they later became worse and he developed a very high temperature. He was heavily sedated and required a tube to help him to breathe (see photograph). He was also treated with oxygen, his temperature was monitored and regulated, lubricants were put in his eyes to prevent them drying, and he was turned every two hours to keep him comfortable and prevent lung collapse.

Jasper required intensive nursing care and monitoring. Over the next day, the dose of sedation was slowly reduced until he regained consciousness.  At this stage, he still had facial and limb twitches. Twenty-four hours later he was greatly improved with fewer mild limb twitches, and he was offered food. The following day Jasper was discharged from hospital.

His owner did not mean to harm Jasper at all and in the future will only use flea products that do not contain permethrin, bought from her vet.

Join the iCatCare Community

Sign up to our monthly newsletter and free e-magazine Intelligent Cat Care

Sign Up