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Chamia Chatman

University of Illinois at Urbana-Champaign

            Currently hundreds of commercial flea and tick products are available for the prevention and treatment of fleas and ticks.  Unfortunately, the brands that contain similar chemicals are thought to be a recurring factor involved in adverse reaction cases reported to the Environmental Protection Agency.  It is also difficult to determine through experimental trials whether or not the chemicals are poisonous or carcinogens.  As such one cannot fully determine the long-term effects of using chemicals such as permethrin or fipronil in conjunction with other chemical compounds to produce pesticides.  This paper will examine some of the common chemicals used for flea and tick products and the current regulation in place to protect pet owners and their companions.

A popular chemical used in pesticides as well as other products was Pyrethrins.  Pyrethrins and Pyrethroids, its synthetic counterpart, were developed as a safer alternative to organophosphates.  Pyrethrins were commonly used in products such as Hartz Dog Flea & Tick Killer, Raid Ant & Roach Killer and Osco Lice Treatment (Pell & Morris, 2008).  Research conducted by the Center for Public Integrity (2008) states, “A Center review of the past 10 years’ worth of more than 90,000 adverse-reaction reports, filed with the EPA by pesticide manufacturers, found that Pyrethrins and Pyrethroids together accounted for more than 26 percent of all fatal, “major,” and “moderate” human incidents in the United States in 2007, up from 15 percent in 1998.”  This data was later proven to be closely related to that of the American Association of Poison Control Centers.  Both reports detailed a significant increase in the number of Pyrethrin incidents reported to their centers.

Further complaints propelled an investigation by the Environmental Protection Agency.  The Office of Pesticide Programs made a formal statement in 2007 that they would expedite their investigation on Pyrethrins after speaking with the Center for Public Integrity.  Initially the investigation being discussed was not to begin until 2010.   Based on the information provided on the Environmental Protection Agency’s website, the registration review decision is “pending” and the case development is “underway”(EPA, 2012).  Since being updated in May 2012, there is still little known about what new safety requirements are necessary for this chemical.  This becomes more evident in the following statement taken from the Permethrin Re-registration Eligibility Decision (RED) fact sheet:

“Permethrin is a member of the pyrethroid class of pesticides. Similar to other pyrethroids, permethrin alters nerve function by modifying the normal biochemistry and physiology of nerve membrane sodium channels. However, EPA is not currently following a cumulative risk approach based on a common mechanism of toxicity for the pyrethroids. Although all pyrethroids interact with sodium channels, there are multiple types of sodium channels and it is currently unknown whether the pyrethroids have similar effects on all channels. Nor do we have a clear understanding of effects on key downstream neuronal function e.g., nerve excitability, nor do we understand how these key events interact to produce their compound specific patterns of neurotoxicity.”  (EPA, 2006)

The document continues to mention that Permethrins have been labeled as “Likely to be Carcinogenic to Humans” due to tumors that developed in mice during a study.  The remainder of this content discusses how health risks can occur worse when ingested.  According to the National Pesticide Information Center (2009), less than 1% of the Permethrin put on human skin will be absorbed.  On the other hand, when it is ingested or inhaled it will be quickly absorbed and will easily pass through the lungs and the rest of the body.

Studies examining the effects of ingesting Permethrin have detailed pregnant rats having offspring that weighed much less and developed extra ribs when compared to the control group.  It also mentions that pregnant rabbits fed Permethrin often had miscarriages and the fetuses that survived were affected by a decrease bone growth.  They also stated,”researchers fed dogs and mice permethrin for up to 2 years and found that their livers increased in weight. The dogs fed permethrin had more tremors than dogs that did not eat it.”  As such the effects from this chemical are not always related to cancer, but other adverse reactions. (NPIC, 2009)

Similarly, the chemicals used on flea and tick collars have been known to cause various health problems in adults and children. Residue levels produced by some flea collars are high enough to cause cancer and damage to the neurological system of children up to 1,000 times higher than the EPA’s acceptable levels (Rotkin-Ellman & Solomon, 2009).  Recently the Natural Resources Defense Council sued major manufacturers of flea collars containing tetrachlorvinphos and propoxur.  Both tetrachlorvinphos and propoxur are toxic chemicals that have been banned, yet are still legally used to control household flea and tick populations.  After the release of the first document created by the National Resources Defense Council, there were six pesticides all containing tetrachlorvinphos and propoxur that were banned.  Due to the lack of regulation in place for the treatment of household flea and tick control, there is a greater chance for them to incorporate unsafe pesticides.

In all, there are numerous cases that can be analyzed further to determine the extent to which certain flea and tick treatments can affect the health of pets and their handlers.  Even the most popular of brands have had customers report about adverse reactions to their pets after applying the product.  At times it is also the pet owner that will have a reaction from the pesticides they applied to their dog or cat.  For example, the quoted text below details a pet owners sadness about the devastating experience of witnessing a beloved companion have seizures.

The owner states, “I am sitting here with tears streaming down my face as I read the information on your web site. I also went to the EPA site and saw that the product I used on our dog is indeed on the list. It is so hard to realize that the seizures that our beloved golden has been experiencing were caused by something I did. In April of 2008 I put Frontline Plus on our dog, within days I noticed a funny jolt that seemed to go through him periodically. This jolting continued to get worse where he would actually drop to the ground each time it happened. We have been through an MRI and multiple tests. He has been on phenobarbital since May of 2008 and the seizures finally appear to be gone. However, he is not the same energetic dog that we had before. He has now been diagnosed with “some kind” of infection that no medication seems to cure. At this point we are talking about quality of life choices with our vet.”  Cases such as this are evidence that the pesticides used need to be further examined to ensure the safety of the pets and handlers.


Environmental Protection Agency. 2006. Permethrin Facts (Reregistration Eligibility Decision(RED) Fact Sheet). Retrieved from

Environmental Protection Agency. (2013). Pyrethroids and Pyrethrins. Retrieved from

Natural Resource Defense Council. Flea and Tick Drops May Be harming Your Pet. (summary literature sheet)

Oregon State University National Pesticide Information Centers. (2009). Permethrin. Retrieved from,

Pell, M.B., Morris, J. ( 2008). ‘Safe’ pesticides now first  in poisonings.  Retrieved from

Rotkin-Ellman, M. & Solomon, G. (2009). Poison on Pets II: Toxic Chemicals in Flea and Tick Collars. Retrieved from


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