Protecting your pet from fleas and ticks is an important part of caring for your pet responsibly. Although there are many brands of over-the-counter flea and tick products available at supermarkets and pet supply stores, it is critical to read their labels, and consult with your veterinarian, before using them on your companion. These products may contain ingredients that could harm pets and children.

In November 2000, the Natural Resources Defense Council (NRDC) released a report called Poisons on Pets: Health Hazards from Flea and Tick Products. The report demonstrated a link between chemicals commonly used in flea and tick products and serious health problems.

The Chemicals

The ingredients to be wary of are organophosphate insecticides (OPs) and carbamates, both of which are found in various flea and tick products. A product contains an OP if the ingredient list contains chlorpyrifos, dichlorvos, phosmet, naled, tetrachlorvinphos, diazinon, or malathion. If the ingredient list includes carbaryl or propoxur, the product contains a carbamate. According to the NRDC, the potential dangers posed by these products are greatest for children and pets. There is reason to be concerned about long-term, cumulative exposures as well as combined exposures from the use of other products containing OPs and carbamates.

The Products

The NRDC's report lists flea- and tick-control products marketed under the following major brand names that have been found to contain OPs: Alco, Americare, Beaphar, Double Duty, Ford's Freedom Five, Happy Jack, Hartz, Hopkins, Kill-Ko, Protection, Rabon, Riverdale, Sergeant's, Unicorn, Vet-Kem, Victory, and Zema. To protect their pets and children, consumers should consult with a veterinarian before purchasing over-the-counter (OTC) products.

The Effects

According to the NRDC, there are studies that show OPs and carbamates can harm the nervous system. Children can be especially vulnerable because their nervous systems are still developing. For pets, the data is limited, but according to NRDC, many companion animals appear to have been injured or killed through exposure to pet products containing OPs. Cats are particularly vulnerable, since they often lack enzymes for metabolizing or detoxifying OPs and can ingest OPs by licking their fur.

What about the EPA?

Each year, millions of Americans purchase over-the-counter flea and tick products believing that they couldn't be sold unless they were proven safe. But the Environmental Protection Agency (EPA) did not begin to review pet products for safety until 1996. There is a substantial backlog of products waiting to be tested, so many pet products containing potentially harmful pesticides still make their way onto store shelves.

Last year, after reaching an agreement with manufacturers, the EPA announced that the OP chlorpyrifos—also known as Dursban—would be on a fast track for a phase-out. A second OP, diazinon, is also on the way out. An agreement between the EPA and manufacturers set the phase out at December 2002 for indoor-use products (including flea and tick products) and December 2003 for all lawn, garden, and turf products.

Reducing the Risks

The HSUS recommends the following precautions be taken to reduce the risks to pets and humans during the flea season:

• Use alternatives to pesticides to control fleas and ticks: Comb your pet regularly with a flea comb, vacuum frequently and dispose of the bags immediately after use, mow areas of the lawn where your dog spends time, wash pet bedding weekly, and wash your pet with a pesticide-free pet shampoo. In addition, to protect cats from fleas and ticks, as well as a host of other outdoor hazards, cats should be kept indoors at all times.

• Always consult a veterinarian before buying or using any flea or tick control product on your pet.

• Never use flea and tick products designed for dogs on your cat, or vice versa.

• Remember never to apply pesticides to very young, elderly, pregnant, or sick animals unless directed to do so by a veterinarian.

• Always read the ingredients, instructions, and warnings on the package thoroughly.

• Avoid OP-based products by looking for any of these active ingredients: chlorpyrifos, dichlorvos, phosmet, naled, tetrachlorvinphos, diazinon and malathion. Avoid products with carbamates by looking for the chemical names carbaryl and propoxur on the label.

• Consider using a product with insect-growth regulators (IGRs), which are not pesticides. These will prevent the next generation of fleas but will not kill insects already on your pet. Common and effective IGR products include those made with lufenuron (found in Program® and Sentinel® and available by prescription), methoprene (in Precor®), and pyriproxyfen (in Nylar® and EcoKyl®).

• You might want to consider several relatively new topical products, available through veterinarians, that are insecticides designed to have fewer toxic effects on the nervous systems of mammals: imidacloprid (found in Advantage®), fipronil (in Frontline® or Top Spot®), and selamectin (in Revolution™).

If you suspect your pet may have suffered negative health effects as a result of a flea product containing OPs or carbamates, consult with your veterinarian immediately. If you think a child has ingested a pesticide, call your local poison control center. Be sure to report all such incidents to the EPA's National Pesticide Telecommunications Network at 800-858-7378.

The HSUS would also like to keep track of these cases.* Please send your contact information, the product name, a brief description of the health problem, and a brief summary of your veterinarian's findings to The HSUS at the following address:

The Humane Society of the United States
Companion Animals Department: Flea Products
2100 L St. NW
Washington, D.C. 20037

Updated May 6, 2008.

*The HSUS will not be able to respond to you personally, but will keep this information on file.