I have read a lot of documentation and legal complaints including class actions against Hartz products, namely their anti-fleas and anti-ticks products which are believed to be potentially dangerous to pets, poisoning them.

So are Hartz product really dangerous or not?


First, understand that Hartz sells a variety of different products with several different active ingredients. Searching the National Pesticide Information Retrieval System for Hartz Mountain Company reveals that the company uses the following pesticides in their products (I sorted them by insecticide class):

  • Synergists with Pyrethroids
    • N-Octyl bicycloheptene dicarboximide (MGK 264)
    • Piperonyl butoxide
  • Pyrethroids
    • Pyrethins
    • Phenothrin (sumithrin)
    • Ethofenprox
  • Organophosphates
  • Growth Regulators
    • Methoprene and S-Methoprene
    • Pyriproxyfen
  • Phenylpyrazoles
    • Fipronil
  • Neonicotinoids
    • Imidacloprid

Several companies use these same chemicals, for example wikipedia explains

Fipronil is the main active ingredient of Frontline TopSpot, Fiproguard, Flevox and PetArmor (used along with S-methoprene in the 'Plus' versions of these products)

So the question to ask is really "Are any of these chemicals harmful?" The answer is yes, pesticides are harmful in certain circumstances.

The EPA performed a study in 2009 and determined

While most people use the products with no harm to their pets, the agency's analysis determined that smaller dogs tend to be disproportionately affected by some products and that the exposure of cats to some dog products is a concern.


EPA recommends that owners consult a veterinarian about the best way to protect their pets from fleas and ticks or whether pesticides are needed, especially before using any product on weak, aged, medicated, sick, pregnant or nursing pets, or on pets that have previously shown signs of sensitivity to pesticide products.

In addition they also determined that they should begin

Restricting the use of certain inert ingredients that EPA finds may contribute to the incidents.

I suspect the "inert" ingredients are the synergists. They have no pesticide properties on their own, but contribute to the affect of pyrethoids. You may choose to avoid products that contain synergists.

Based on this information, when choosing to use a flea/tick medication for your pet, you can take precautions based on these findings:

  • Read the label carefully for cat/dog use
  • Read the label carefully for the size of pet you have
  • Follow the application instructions precisely
  • Never combine/split dosages, only use the right dosage for your pet
  • Test a small amount of a new product on your pet to check for sensitivity
  • Talk to your vet to determine if a flea/tick medication is appropriate for your pet
  • Research the active ingredients to determine if its a type of medication you want to use

For the last point, The National Resources Defense Council performed a study in 2000 (Poisons on Pets) that noted the use of organophosphates is particularly toxic to pets, children, and even adults. One example they gave is

Dipping or powdering pets with tetrachlorvinphos. EPA determines that powdering or dipping a single pet with tetrachlorvinphos just twice a year would, over the course of a lifetime, pose a risk of cancer to the person dipping the pet nearly six to seven times higher than acceptable EPA levels. Dipping or powdering multiple pets, or doing so more frequently, would raise cancer risks even higher.

Most of the organophosphates reviewed in this study have been removed from the market by the EPA, but tetraclorvinphos is still in use (as the trade name Gardona). The authors recommend avoiding it.

The authors also recommended avoiding carbamates (urethanes) because they are chemically similar to organophosphates. None of the chemicals currently in use by Hartz (according to my research at the EPA's site) are carbamates.

Finally, the authors do give some suggestions on safer alternatives to these pesticides:

Easy physical measures alone, like frequent washing and combing of the pet and vacuuming carpets and furniture, can bring mild flea infestations under control. Alternatives include insect growth regulators, or IGRs, which are not pesticides, but rather chemicals that arrest the growth and development of young fleas. These include methoprene, fenoxycarb and pyriproxyfen and the popular lufenuron (Program®). Alternatives also include newer pesticide products sprayed or spotted onto pets, such as fipronil (Frontline®) or imidacloprid (Advantage®)

Note: Noeonicotinoids (like Imidacloprid) are suspected in playing a role in colony collapse disorder. In addition, Fipronil has been linked to bee deaths. While this isn't a health issue for your pet, you may want to consider it when selecting a pesticide.

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