The Best Flea and Tick Prevention for Dogs: Know What to Avoid


Reader’s Note: This post was originally featured in Dogs Naturally Magazine

Your Dog And Toxic Flea And Tick Prevention

The advent of easy to use spot-on products has made flea and tick prevention convenient for many pet owners. Certain ticks can carry dangerous diseases so we’ve all become extra careful with our prevention routine.

As a veterinarian, I’ve been taught that the majority of these products are harmless and safe, but evidence now shows that both the ‘active’ and some ‘inactive’ ingredients in the spot- on preparations have been linked to serious health effects both in laboratory animals and in pets.

The Washington-based Center for Public Integrity (CPI), a nonprofit investigative news organization, and the National Resources Defense Council, an environmental advocacy group, have both published reports about the safety of prescription and over-the-counter flea and tick treatments.


Dr. Dobozy of the EPA’s Pesticide Division has found that the active ingredient (fipronil) in Frontline remains in a pet’s system with the potential for nervous system and thyroid toxicity. Tests on laboratory animals resulted in thyroid cancer and altered thyroid hormones, liver and kidney toxicity, reduced fertility and convulsions. Frontline’s web site creates the impression that the product stays in the oil glands of the skin. But Dr. Dobozy’s study showed that, in fact, it does enter the body and the organ systems.


Advantage contains the active ingredient Imidacloprid. In laboratory studies Imidacloprid has been found to increase cholesterol levels in dogs, cause thyroid lesions, create liver toxicity, and has the potential for damaging the liver, heart, lungs, spleen, adrenals, brain, and gonads.

As a neurotoxin, it can cause incoordination along with labored breathing and muscle weakness. When this drug was tested after its introduction in 1994, researchers found an increase in the frequency of birth defects when it was tested on rats, mice and dogs. In the Journal of Pesticide Reform, author Caroline Cox exposes thyroid lesions as a result of exposure to imidacloprid.


Most people think that the pyrethrins (naturally occurring compounds from the chrysanthemum plant) and pyrethroids (the synthetic counterpart) are less hazardous than other tick and flea preventive ingredients.

However, data from pyrethroid-based insecticides was recently made public through the Freedom of Information Act and analyzed by CPI. According to CPI, from 2002 through 2007, at least 1,600 pet deaths related to spot-on treatments with the above mentioned ingredients were reported to the EPA. That was nearly double the reported fatalities linked to flea treatments without pyrethroids.

The pyrethroid spot-ons also accounted for more than half of the “major” pesticide pet reactions including brain damage, heart attacks and seizures. Non-pyrethroid spot-on treatments accounted for about 6 % of all major incidents. Bio Spot Flea and Tick Control, Defend EXspot Treatment and Zodiac FleaTrol Spot On all contain either or both of the active ingredients Permethrin and/or Pyriproxyfen.

Permethrin has been implicated as a carcinogenic insecticide causing lung cancer and liver tumors in laboratory animals. There is also a suspicion that it disrupts endocrine function. It can act as a neurotoxin, causing tremors as well as increased aggressive behavior and learning problems. Vectra #D, the new guy on the block, contains 36.08% Permethrins.


As a result of all this newly revealed information in the CPI’s report, the EPA in April 2009 announced it was taking a closer look at all spot-on flea and tick products. Not long after, in July of the same year, the EPA released a follow-up advisory warning people to be cautious when using flea and tick prevention products. The EPA also said it would be taking action to address uncertainties about the so-called ‘inert’ ingredients present in these products.

Safe alternatives are very much needed for flea and tick control. Medical problems that have become common in our dogs could potentially be linked to these previously “believed to be innocuous” spot-on products.


Even now, more than a decade later, there are still questions surrounding the safety of certain flea and tick prevention products, to the extent that the FDA continues to maintain a page to provide guidance on how to safely use these types of products.

In short, when it comes to using flea and tick prevention products, they recommend:

Carefully Selecting a Product

Speaking to a veterinarian is key. They can advise you on which products are well regarded, and also take into account complicating factors like the breed, weight, and age of your dog, as well as any illnesses and medications that are considerations for your dog’s health.

Following Instructions Precisely

The brief time you spend reading a product label could save you considerable stress later. Always read the label – even if you’ve used the product in the past – and be sure to closely adhere to the directions about how much of the product to use and how often to use it.

Monitoring Your Dog After Use

If your dog has an adverse reaction to the product, you want to be able to catch the issue as soon as possible. In the event that you notice signs of trouble in your dog, you’ll want to call your veterinarian and follow their instructions on how to respond to the situation.

Elisabeth Weiss is a highly certified, experienced dog trainer in Manhattan, NYC. To learn more about dog training services, contact us by phone at (917) 783-1473 or our contact form.

Related Posts /