WARNING! The Hidden Dangers of Flea and Tick Medications

WARNING! The Hidden Dangers of Flea and Tick Medications

Flea and ticks are pests I think we all can all agree we can do without, they’re creepy, crawly and they spread diseases. Unfortunately, ticks are part of our lives, and chances are you’ve seen a flea or tick in your lifetime, especially if you have a dog.

No one wants to find a tick on their dog, so we listen to our vet and purchase the flea and tick products based on their recommendations. Frontline Plus, K9 Advantix II, NexGard, Seresto are all commonly available from your vet, online or in the pet stores.

But did you know the active ingredients in all of these products are pesticides? Yes, you read that correct, you are putting poison on your dog! Yikes, scary right?

How can these companies get away with marketing a poison to pet owners? They all say the amount is slow-releasing in small amounts and are perfectly safe for your dog. Really? Would you put pesticides on yourself or your kids?

WARNING! The Truth About Flea and Tick Medications

UPDATE: 9/20/18 from the FDA: Animal Drug Safety Communication: FDA Alerts Pet Owners and Veterinarians About Potential for Neurologic Adverse Events Associated with Certain Flea and Tick Products

On the list of products the FDA is warning us about are Bravecto, Credelio, Nexgard and Simparica. Some pets have experienced adverse events such as muscle tremors, ataxia, and seizures.

Safety Warning for Flea and Tick Meds

Even the K9 Advantix box warns that it is hazardous to humans and fatal to cats! Here is a photo I took of the box of K9 Advantix I bought last year. More than half of the box are hazard warnings! Notice how they attempt to distract you from those warnings by putting the benefits in red. Yikes, do I really want to put this on my dog?

K9 Advantix Warnings

Click to enlarge and read!

If you Google the brand you use and side effects, you can read story after story on how dogs have had severe reactions to this stuff. Some as simple as skin irritation but many as serious as seizures or death.

Now, of course, there are many dogs that don’t have any visible side effects, but how do we really know that they aren’t experiencing any long-term medical issues from this pesticide we are intentionally exposing them to?

What Are the Active Ingredients in Flea and Tick Products?

We’ve used both Frontline Plus and K9 Advantix on our dogs. I’m embarrassed to admit, I never looked at the back of the boxes until a few years ago. After reading something online, I started researching and it didn’t take long for me to realize this stuff is slowly killing our dogs.

Even the Humane Society of the United States warns us about the use of these chemicals on our dogs! “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.”

I’ve researched each of the top-selling flea and tick products. Found their active ingredient list from their website and put it all together here for you to make your own informed decision.

Scary fact: I found all the ingredients listed on these flea and tick medications on the National Pesticide Information Center.Click to Tweet Source: National Pesticide Information Center

Frontline Plus


Ingredients: Fipronil, (S)-methoprene

Fipronil is a broad use insecticide that belongs to the phenylpyrazole chemical family. Fipronil is white powder with a moldy odor, used to control ants, beetles, cockroaches, fleas, ticks, termites, mole crickets, thrips, rootworms, weevils, and other insects.

Methoprene is used against insects. It comes in two different forms called s-methoprene and r-methoprene, and s-methoprene is the one that behaves like an important hormone in insects. It can be used against fleas, flies, moths, beetles, and other insects.

K9 Advantix II


Ingredients: Imidacloprid, Permethrin, Pyriproxyfen

Imidacloprid is an insecticide that was made to mimic nicotine. Nicotine is naturally found in many plants, including tobacco, and is toxic to insects. Imidacloprid is used to control sucking insects, termites, some soil insects, and fleas on pets.

Permethrin is an insecticide in the pyrethroid family. Pyrethroids are synthetic chemicals that act like natural extracts from the chrysanthemum flower. Permethrin is used in a number of ways to control insects. Products containing permethrin may be used in public health mosquito control programs. They may be used on food and feed crops, on ornamental lawns, on livestock and pets, in structures and buildings, and on clothing. Permethrin may also be used in places where food is handled, such as restaurants.

Pyriproxyfen mimics a natural hormone in insects and disrupts their growth. It is a type of insect growth regulator that affects mostly young insects and eggs. Pyriproxyfen affects many types of insects, including fleas, cockroaches, ticks, ants, carpet beetles, and mosquitoes.
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Ingredients: Afoxolaner has the chemical composition 1-Naphthalenecarboxamide, 4-[5- [3-chloro-5-(trifluoromethyl)-phenyl]-4, 5-dihydro-5-(trifluoromethyl)-3-isoxazolyl]-N-[2-oxo-2-[(2,2,2-trifluoroethyl)amino]ethyl.

From what I can tell Afoxolaner was created specifically for use in NexGard? So that is why they have the breakdown of what the composition of the chemicals is, the only chemical I could find is Naphthalene carboxamide.

Naphthalene is an aromatic hydrocarbon found in coal car or crude oil. Naphthalene is used in the manufacture of plastics, resins, fuels, and dyes. It is also used as a fumigant insecticide that works by turning directly from a solid into a toxic vapor. This process is called sublimation. Most products containing naphthalene in the U.S. are used to control clothes moths in airtight containers.



Ingredients: Imidacloprid, Flumethrin

Imidacloprid is an insecticide that was made to mimic nicotine. Nicotine is naturally found in many plants, including tobacco, and is toxic to insects. Imidacloprid is used to control sucking insects, termites, some soil insects, and fleas on pets.

There it is in black and white, each one of these popular flea and tick products that are recommended to use on our dogs contains insecticides. Do you still feel it’s okay to protect your dog with these chemicals?

If you are wondering if heartworm preventative is safe, same rules apply. Check out The Truth About Heartworms By Only Natural Pet.

Side Effects of Flea and Tick Medication

  • Vomiting
  • Diarrhea
  • Lethargy
  • Weakness
  • Staggering
  • Disorientation
  • Hypothermia
  • Abdominal pain
  • Light or severe depression
  • Allergic reactions, such as rashes and itching

Is It Possible to Protect Your Dog from Fleas and Ticks with Natural Ingredients?

I will admit, I’m scared to NOT protect my dogs from fleas and ticks. Our foster dog, Taylor had Lyme disease, which is contracted from being bit by an infected tick. And now that we will be living in a rural area that is known to have ticks, I need to make sure I protect my dogs and family.

So I began searching for natural flea and tick prevention for our dogs. From homemade flea and tick prevention with essential oils to natural products available to purchase online.

I’ve ordered several options from Only Natural Pet and will be testing on our dogs to see what works best over the next few months. I will make sure to report back with my findings. Until then, follow me on Facebook to see updates throughout the summer.

So How Can We Protect Our Dogs from Fleas and Ticks?

Should you continue using Frontline Plus or K9 Advantix? I don’t have the right answer for you. You aren’t a bad dog parent if you decide to use these products, we all need to make our own decisions and do what is best for our dogs. No judgement from me. But now that you know the facts, I’d love to hear what you decide to use to protect your dog from fleas and ticks. Will you continue to use the pesticide products, or try something natural?

Please comment below with what works for you and your dog, it will help others in the Rescue Dogs 101 community to make an informed decision.

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About the Author Debi@RescueDogs101

Debi McKee is a mom of three kids, two dogs and the creator of Rescue Dogs 101... where she guides you in your journey of adopting and raising a rescue dog every step of the way. She also volunteers for a local dog rescue and Humane Society.

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