It was a highly panicked Elsie Trent who called her local veterinary surgery on a Wednesday afternoon. She’d just realised she’s applied the wrong spot-on flea product to her cat, Tabitha. She had applied the product about an hour ago and only just realised when she spotted that Tabitha was drooling heavily, seemed agitated, was walking oddly and had checked the packaging. She’d applied a spot-on intended for her dog, a Border Terrier. 

The fab veterinary receptionist team understood the importance of this error and advised Elsie to bring Tabitha straight to the surgery, along with the packaging of what product she’d applied to Tabitha. It was highly likely that Tabitha was suffering from permethrin poisoning as a result of the accidental application of a dog anti-parasitic.

What is permethrin?

Permethrin is a pyrethroid – a synthetic pyrethrin. Pyrethrins are insecticides, naturally found in Crysanthemum flowers and used in some flea spot-on products. They are commonly used in dog products at high concentrations. They are occasionally used in cat products, including flea collars and shampoos, but at much lower levels. And they can also be found in domestic garden insecticide products. 

The veterinary team were waiting for Elsie and Tabitha when she arrived shortly afterwards. After an examination of both cat and packaging, the vet confirms that Tabitha is likely suffering from permethrin toxicity. And the veterinary nursing team take Tabitha straight out to be washed off whilst the vet talks to Elsie. Time is of the essence!

Symptoms of permethrin toxicity

Pyrethroid toxicity in cats is very serious, and can be life-threatening. If any of these signs are seen, an urgent trip to the vets is recommended. 

  • Excessive salivation
  • Agitation/excitement
  • Vomiting
  • Uncoordinated/wobbly walking, difficulty standing or moving (ataxia)
  • Twitching and tremors
  • Seizures
  • Changes to body temperature
  • Difficulty breathing

The vulnerability of cats

The vet explained that cats react differently to some drugs than dogs do, which is why permethrin is poisonous to cats but not dogs. Cats lack certain enzymes which break down chemicals, so the permethrin builds up in the body and does harm. Elsie was horrified that she had applied the spot-on, but the vet reassured her that it was an accident, and that Tabitha was in the right place. She advised that Tabitha was being washed with diluted washing up liquid as they spoke, to remove any product still on the skin, and would then be reassessed.

Tabitha was examined further after being thoroughly washed off

She had a slightly elevated body temperature and some intermittent muscle tremors and twitching. The vet recommended that Tabitha was admitted to the hospital for close monitoring and to keep control of her muscle tremors. She gave an estimate for two days of close monitoring and hospitalisation. Elsie was worried about the costs but knew that Tabitha needed the treatment. Thankfully, Tabitha was insured, and the vet reassured Elsie that costs should be covered even though Elsie had applied the product, as it was a complete accident – and a very common toxicity in cats.

Treating permethrin toxicity

Affected cats, if stable, are first washed with soap or a detergent to remove any product on the skin, before it can be absorbed. There is no specific treatment or antidote for this toxicity. Supportive treatment for specific symptoms such as tremors, seizures and breathing difficulties is indicated. Patients are usually hospitalised for a few days for close monitoring of parameters such as body temperature and kidney function, alongside supportive care. Severely affected cats may need a treatment of a lipid infusion, which helps to absorb permethrin from the system. 

Tabitha remained stable in the hospital

Her twitches and tremors gradually reduced over the next 24 hours and her temperature stabilised. She was discharged home to a very grateful Elsie, who was feeling extremely guilty. The insurance company paid for all costs, leaving Elsie to only pay her excess – and a large pet shop bill for all the treats she bought Tabitha to aid her recovery! 


Permethrin poisoning is one of the most common toxicities seen in cats. Luckily, the majority of cats will make a full recovery if seen promptly by a vet and treated. 

Tabitha’s owner made a common mistake, and now checks and double checks the packaging before applying any products to her pets. Always use medicines which have been prescribed for your individual pet and seek advice from a vet if you’re unsure about any medication. If you have a dog and a cat, try to use products without permethrin for your dog, or separate the pets for 72 hours after application. Never use dog products on cats.