Flea Products for Your Cat: Use Extreme Caution

Fleas. The plight of the household pet. Fleas are frustrating and annoying insects that thrive on our pets and make them miserable. But getting rid of these pesky creatures is often a difficult process. If you use a commercial product on your cat, it is critical that you take extreme caution by using only products designated for cats.

Today, many products are available to reduce the flea population within our homes and on our pets. Common traditional insecticides include flea powders, shampoos and sprays. And a popular alternative is the "spot-on" flea product that comes in a tube and is applied in small amounts to the animal's back or neck, usually once a month.

The most common types of insecticide used to kill fleas are pyrethrins. These products are derived from the Chrysanthemum flower. When used according to label directions, pyrethrins are relatively safe and very effective. Synthetic insecticides have more recently been formulated to increase strength and effectiveness. Permethrin is a synthetic pyrethrin.

Pyrethrins work by paralyzing the nervous systems of insects, and kills insects by direct contact and by ingestion. It also has repellant properties and is effective against all stages of insect growth, particularly larvae.

Toxicity related to pyrethrins is usually associated with applying much more of the product than is safe for your cat. Permethrin-based topical flea products have a much greater potential for toxicity and are usually labeled "for use in dogs only." Severe illness and fatalities can occur in cats when their owners apply these products. Use extreme caution: dogs use a concentration of permethrin that ranges from 45 to 64 percent. However, this can be lethal to a cat, which can tolerate only concentrations of 2 percent.

Cat owners should read labels carefully before purchasing any flea or tick product. If a product says it is for use only on dogs, then it should NEVER be used on cats – even in small amounts. Just a few drops can result in severe illness or death. If you also own a dog, your cat can become ill just by being close to your permethrin-treated dog.

What To Watch For

Application of permethrin-based insecticide to a cat will usually result in toxic signs within 6 hours. If your cat exhibits these symptoms, quickly bathe your pet in mild dishwashing detergent and call your veterinarian.


The diagnosis of permethrin or pyrethrin toxicity is based on physical exam findings as well as a recent history of topical flea product application. Skin and hair tests can be done to confirm the presence of insecticide, but those results may take several days.


If your cat exhibits signs of permethrin or pyrethrin toxicity, bathe him in a mild dishwashing detergent to remove flea product from your pet's skin, thereby reducing the amount absorbed. Do not use flea shampoo and do not use hot water since that will dilate blood vessels in the skin and increase the absorption of the flea product. Then call your veterinarian; additional treatment is probably required. Your veterinarian will probably recommend hospitalization with continuous intravenous fluids.

For seizure control, your veterinarian may use diazepam or phenobarbital. And to treat muscle tremors, methocarbamol may be given multiple times throughout the hospital stay.

If treated early, the majority of cats suffering from permethrin/pyrethrin toxicity recover enough to go home within 24 to 48 hours, although fine muscle tremors may continue for several days.

The best way to prevent toxicity to flea products is to read the labels and follow the directions. If a product is labeled "for use in dogs only," DO NOT USE IT ON YOUR CAT. Cats have different metabolisms from dogs and are much more sensitive to certain medications, drugs or toxins.