Flea and Tick Medication Poisoning (Pyrethroid Toxicosis) in Cats


Cats are particularly sensitive to many flea and tick medications, and exposure to formulations that are not specifically approved for feline use can be fatal. Cats must be treated only with veterinarian-approved products specifically labeled for safe use in cats to minimize the risk of toxicity. 

Most cases of flea and tick medication poisoning in cats result from exposure to a permethrin-based product, so the resulting syndrome is often called by the general term pyrethroid toxicosis.  Cats with pyrethroid toxicosis require immediate medical attention. Symptoms of pyrethroid toxicosis include  muscle tremors, and seizures. Symptoms can take up to 72 hours to develop after exposure to the medication. Diagnosis is made based on a history of exposure to these medications. 

Most cats with pyrethroid toxicosis recover with no long-term effects as long as the condition is recognized early and treatment is aggressive.  Left untreated, cats can suffer from severe complications including brain damage, muscle damage and kidney failure.

Risk Factors

Certain flea and tick medications are potentially fatal to cats, even in small amounts and even if they are labeled for use in cats. If a cat has been exposed to the following drugs, they require immediate medical attention:

• Any product labeled for use only on dogs

• Permethrin • Pyrethrin • Flumethrin • Allethrin • Bifenthrin • Cinerin I & II • Cyfluthrin • Cyhalothrin

• Cypermethrin • Cyphenothrin • Deltamethrin • Etofenprox • Fenvalerate • Fluvalinate • jasmolin I & II • Phenothrin

• Resmethrin • Sumithrin • Tefluthrin • Tetramethrin • Tralomethrin

The active ingredient in the flea and tick medication can be found on the product packaging, usually under the brand name.

Possible Causes

Most cases of flea and tick medication poisoning in cats are from exposure to permethrin-based products, so the clinical syndrome is often called “pyrethroid toxicosis”. Cats are highly sensitive to permethrin, and even small amounts are potentially fatal. 

Cats often develop this toxicosis when owners mistakenly give dog-only medications to their cat. It is critical to follow all instructions on the label, and to only use veterinarian-approved medications in cats. Never use a dog-only product on a cat.

Cats may also be exposed if a pyrethroid product is applied to the skin of a dog living in the same home. To prevent this, select cat-safe medications for dogs living with cats and separate the dog from the cat(s) until topical flea medications are dry.

Main Symptoms

Cats with pyrethroid toxicosis typically  show symptoms like:

Muscle tremorsSeizures • Hypersalivation (ptyalism) • Hypersensitivity (paresthesia) • Vomiting

It can take up to 72 hours for symptoms to develop after exposure to medication.

Detailed Characterization

Symptoms of mild pyrethroid toxicosis are usually limited to:

• Excessive salivation • Ear twitching • Quiet demeanor • Mild skin irritation

With moderate to severe cases of pyrethroid toxicosis, cats may experience:

VomitingDiarrheaPanting • Ear- and paw-flicking • Wobbly, uncoordinated gait (ataxia) • Muscle tremors


Other symptoms associated with pyrethroid toxicosis include: 

Trouble breathing (dyspnea)Rapid breathing (tachypnea)Loss of consciousness • Coma

Testing and Diagnosis

Diagnosis of pyrethroid toxicosis typically relies on a known exposure to these medications. It is uncommon to conduct a specific test to confirm exposure. 

Treatment may involve any or all of the following:

• Bathing the cat to remove the medication, if applied to the skin • Anti-seizure medications • Muscle relaxants • Fluid therapy

• General anesthesia when seizures cannot be controlled through medication alone • Intravenous lipid emulsion (ILA) therapy

When serious symptoms are present, they are managed prior to bathing because bathing can make tremors worse or trigger a seizure.

Steps to Recovery

Symptoms of pyrethroid toxicosis in cats generally resolve within 2-3 days with prompt and aggressive treatment and the prognosis for full recovery is good. Pyrethroid toxicosis is life-threatening, so without treatment, brain damage, muscle damage, kidney failure, and death may result.


Pyrethroid toxicosis is prevented by keeping cats on a vet-approved flea control medication specifically for use in cats. It is also prevented by ensuring the treating veterinarian is aware of the presence of cats in the home when sourcing flea control products for other animals, especially dogs.

Is Pyrethroid Toxicosis Common in Cats?

Pyrethroid toxicosis is rare in cats receiving veterinarian-approved flea and tick products specifically for feline use. 

It is commonly reported when cats exposed to pyrethroids in/on: 

• Over-the-counter products • Products labeled for dogs • Dogs treated with pyrethroids

Typical Treatment

• Bathing • Anti-seizure medication • Muscle relaxants

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