The Humane Society of the United States
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Flea and Tick Product Ingredients: What You Should Know

Read this before buying flea and tick products for your pet

You can find many brands of flea and tick products at supermarkets, pet supply stores, online retailers, and through your veterinarian. Before you use any of these products on your pets, it is critical to read their labels and consult with your veterinarian. They may contain ingredients that could harm pets and people. 

The studies

The Center For Public Integrity released information on its website for its Perils of the New Pesticides study in 2008. At least 1,600 pet deaths related to spot on treatments with pyrethroids were reported to the EPA over the last five years, according to an analysis of EPA pesticide incident exposure data by the center. The EPA assigns risk levels to all pesticides for their potential dangers to humans and some flea and tick products contain chemicals, specifically permethrins, that are "likely to be carcinogenic to humans."

Learn how to recognize the symptoms of poisoning by flea and tick products

The center reported that pyrethroid spot-ons also account "for more than half of 'major' pesticide pet reactions reported to EPA over the last five years—that is, those incidents involving serious medical reactions such as brain damage, heart attacks, and violent seizures. In contrast, non-pyrethroid spot on treatments accounted for only about 6 percent of all major incidents."

The Center For Public Integrity's study said pyrethroid-based flea and tick treatments are approved for sale by the EPA, and they are readily available in powders, shampoos, dips, sprays, and other forms,  "but they are also linked to thousands of reported pet poisonings, and they have stirred the ire of pet owners, the concern of veterinarians, and the attention of regulatory agencies."

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

Organic Treatments on

The chemicals

Besides pyrethroid-based products, ingredients to be wary of are organophosphate insecticides (OPs) and carbamates, both of which are found in various flea and tick products.  The only OP currently found in flea and tick products in the U.S. is tetrachlorvinphos.  This chemical is classified by the EPA as being "likely to be carcinogenic to humans."  There are questions about the effects of long-term, cumulative exposures as well as combined exposures from the use of other products containing OPs and carbamates.  Permethrin is another chemical that the EPA has classified as "likely to be carcinogenic to humans" if ingested orally. 

If the ingredient list includes carbaryl or propoxur, the product contains a carbamate.  According to the NRDC, the potential dangers posed by thee products are greatest for children and pets.  Propoxur is considered to be a "probable human carcinogen" by the EPA.  As of September 2010, Carbaryl will no longer be permitted for use in new pet products.  However, existing stock of flea/tick products containing carbaryl can still be sold.  The HSUS recommends that pet products containing carbaryl should be disposed of and not used on pets.

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 flea and tick products believing that they couldn't be sold unless they were proven safe. But the EPA did not begin to review pet products for safety until 1996.  As noted on CPI's website, "The EPA cannot make its own assessment because unlike the regulations directing the FDA's approval of human products, the Federal Insecticide, Fungicide and Rodenticide Act does not require pet products to undergo field trials prior to approval.  So the agency can only require less extensive testing, often only on one breed of dog or cat.  This makes it difficult to predict the effects on the broader population of users."

If you do decide to use flea and tick products

Follow these simple steps to help prevent problems:

  • Never use dog treatments on cats, and vice versa
  • Always be certain of your pet's weight before purchase to ensure proper dosage
  • Don't split one "large dog" dose in half for two small dogs (or combine two "small dog" doses for one large dog)
  • Read and follow all instructions when using these products
  • Do not use these products on elderly or pregnant animals

 How to tell if your pet has been poisoned

Symptoms of poisoning by flea/tick treatments may include salivating, dilated pupils, tremors, vomiting, hiding, shivering, and skin irritation.

What to do if your pet has been poisoned

If you suspect your pet may have suffered negative health effects as a result of a flea product, 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, or follow these steps to report an animal exposure or illness »

Let us know

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
1255 23rd Street, NW, Suite 450, Washington, DC 20037

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