Pesticides in Pet Products: Why Your Dog or Cat May Be at Risk

By M.B. Pell and Jillian Olsen, The Center for Public Integrity. Posted February 2, 2009.

Warning Signs

A few websites, run by pet owners, specialize in educating people on the dangers of over-the-counter spot on treatments. Almost every day someone posts a new horror story, often involving a late-night emergency trip to the vet. "I cannot stop crying knowing that if I hadn't put that on them then they would still be here playing and loving as they always did before," reads one post about a woman's loss of two kittens in October.

Ellie, a mini dachshund from La Vernia, Texas, suffered chemical burns where Bio Spot flea and tick drops were applied to her back. Credit: Michele Worcester.

The concentrations of pyrethroids in over-the-counter spot on pet treatments range from a 40 percent to an 85 percent solution, eight to 17 times stronger than the strongest pyrethroid product currently approved for use on humans. Neither the EPA, which generally regulates topically applied products, nor the Food and Drug Administration, which generally regulates orally applied pet products, has a product registered for human application containing a pyrethroid concentration above 5 percent, and that FDA-approved product requires a doctor's prescription. In fact, the Sergeant's Gold Squeeze-On for Dogs warning reads: "Harmful if swallowed or absorbed through skin," while the application portion of the label directs people to apply the treatment "to the dog's skin."

But these high concentrations may be necessary in pet products because pets are more apt to come in contact with fleas and ticks, according to Margaret Rice, chief of the EPA's Office of Pesticide Programs registration branch. Some human products, like the 5 percent permethrin shampoo, also call for more of the product to be applied than the just under one ounce in the spot on treatments.

Pyrethroid toxicity targets nerve and muscle cells in pets, according to a study published in The Veterinary Journal in June 2008. The study found that dermal exposure by application to the skin or coat is the most common route of toxic exposure, potentially causing hyperexcitability, tremors, profuse salivation, and seizures. The seizures can result in brain damage or, less frequently, death.

Representatives of Central LifeSciences, the parent company of Farnam, the distributor of Bio Spot, said that they could not discuss the death of Wings because their investigation of the incident is still underway. The company said reports of adverse reactions are rare, about three of every 10,000 doses for cat products and five of every 10,000 doses for dog products. These numbers include incidents that resulted from misapplication and preexisting medical conditions, according to Central LifeSciences. "Bio Spot Spot On Flea & Tick Control for Dogs has met all applicable EPA registration requirements and is approved for topical use on dogs," the company said in a letter they sent in July to one unhappy customer whose dog had recently died.

"Even if it is owner error much of the time, something is not working the way it should be," said Stephanie Shain, director of outreach for the Humane Society of the United States.

Hartz Mountain Corp. representatives said via e-mail that the active ingredient in the company's spot on dog treatments, the pyrethroid d-phenothrin, and the active ingredient in their cat product that kills adult fleas, the pyrethroid etofenprox, are categorized as least toxic by the EPA, as opposed to the active ingredient in Frontline, fipronil, and the active ingredient in Advantage, imidacloprid, which, while much less concentrated, are rated as moderately toxic. Sergeant's cat spot on treatments also contain etofenprox, but the company has spot on dog products that contain cyphenothrin and products that contain permethrin, moderately toxic pyrethroids.

Another possible explanation for the number of incidents is that consumers often misuse flea and tick products, causing the sickness that pet owners later blame on the treatments, said Jennifer Windrum, a spokeswoman for Sergeant's. "Pet owners feel incredibly guilty if they misapply it to their pet," Windrum said. "It's easier to blame a company." Common misapplications include applying more powerful dog products to cats, applying the product where the pet can lick it, and using a treatment meant for a large animal on a small one. The directions on these products include a description of where to apply, sometimes a diagram, and if it's a dog product, multiple warnings not to it use on cats.

Forest Desmond and his wife Marilynn received a letter from Sergeant's offering to pay their $125 vet bill after they applied Sergeant's Gold Squeeze-On for Dogs to their five dogs. The letter from Sergeant's also stated that the company believed the dogs may have licked the product off each other, a violation of the application instructions. "The Sergeant's Gold Squeeze-On for Dogs is for external use only and has several warnings on the package indicating such," the letter says. The product's label does not instruct consumers to keep dogs separated after treatment, but Sergeant's has submitted a request to the EPA to have the label changed. Sergeant's "Look at the Label" website already recommends people separate their pets after application.

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