Dangers of Flea Medication

By Andie Francese


Flea and tick medications are common treatments for pets. They are often sold over the counter and applied to millions of pets ever year; however, flea medication carries a myriad of risks to both pets and owners. The medications are filled with toxic chemicals (they kills fleas and ticks, after all). If they are not applied to extreme caution, serious complications and possibly death may occur.


Flea medication is highly concentrated; when rubbing the medication onto an animal, high concentrations can be left on one spot on the dog or cat. The high level in one are then seeps into the skin and into the pet's circulatory system. The toxins that are used to kill fleas are also harmful to the animal . Uneven application can cause nerve problems and can make both dogs and cats extremely ill with lasting effects.


Many flea medications come in shampoo form. The theory is that the flea medication will be applied and then rinsed from the animal. It is imperative to rinse the pet thoroughly, as dogs and cats tend to lick themselves and any medication residue could be ingested. The toxins in flea medication, even if just residue, can lead to nerve damage, brain damage and may be fatal for pets.

Human Contact

Any people using a flea medication on their pets also must be extremely careful when handling the products. Hands must be washed thoroughly afterward and skin contact should be limited. The toxic chemicals used to kill fleas can seep into the skin and cause unpleasant reactions in some people. .

Puppies and Kittens

Flea medication should not be used on kittens and puppies. The young animals are not big enough or strong enough to defend against the chemicals and may end up with brain damage, kidney damage and nerve damage if the product is not applied correctly.


Flea medication designed for dogs has been used on cats by some owners as the labels are not always clear, but the concentration of the chemicals designed for dog fur tend to seep more quickly and at higher levels into a cat's fur, and can cause serious neurological problems.
Comments (21)
Jul 16, 2009 DogLuva595
Oh wow! I did'nt really know that! We've been applying Flea Medicane to our dogs for years, and we never knew we had to be this cautious! This new topic was very helpful. :)
Aug 1, 2009 jenhocutt
I have two small min pins and don't like the fact that I have been using frontline/advantage on them as a precautionary step to prevent fleas. They have never had fleas. What are the alternatives to using dangerous chemicals on my pets??
Sep 20, 2009 hutton
3years ago i went all natual. and started using flea free, it repels fleas ticks and mosquitos.its a food works without toxic chemicals most pets have a short lifespan.lets not put poison on em!
Jan 11, 2010 EastCoastWestie
I use garlic. Yes, garlic has the smae toxin as onions, but it is in such small amounts you would have to feed massive amounts to do any damage. Garlic strengthens the heart, relieves respiratory problems, is antibacterial, antifungal, and antiviral, it is a natural intestinal cleaner, prevents fleas, ticks, mosquitoes, and other parasites, including worms. Most dogs do not like the taste of fresh, raw garlic, so I use 1000 mg garlic oil softgels (dry garlic pills do not have the same effect.) Give a dog under 25 lbs 1 softgel per day, 25 lbs-50 lbs 2 per day, 50 lbs to 75 lbs 3 per day, and so on. I wrap them in cream cheese and my Westies never know. Never have we found a single flea while using garlic.
Jul 24, 2010 blstarlin
I work at a Vet Hospital in NC where we have flea/ tick problems year round and not just the summer time. We recommend prevention every month (this includes Advantage multi/ Advantix/ Vectra/ Frontline etc). The product actually does not soak into their circulatory system as stated above, it actually is just absorbed into the skin layers and spreads out using the oils from the skin. And I agree you need to make sure you are applying it correctly (be sure to read the box for exact directions) otherwise it can be harmful to pets. Just thought I would leave a comment and let you all know, it is safe to use flea/tick preventions especially since they can acquire so many diseases if they are not protected. All this information has come from directly talking to the companies that make these products
Mar 25, 2011 kalypso216
My 7 month old Siberian Husky died on tuesday. I had him at the vet a week before because he was acting strange. The first question my vet asked was if I had been treating him for flea. I had been. I was unaware that it could have such severe effects on Northern breeds. It started by giving him head aches and then he had a seizure which fried his brain. He could no longer breath on his own. I had to "pull the plug" on my puppy because the product that was supposed to keep my dog safe from fleas and the diseases they carry, killed him.
May 19, 2011 mama4
Dear kalypso216, So sorry you lost your beloved pet. I wish someone had told you earlier of the dangers. I had no idea either until three years ago we almost lost our 7 yr old daughter due to flea meds, according to our doctor. We had been to an animal shelter 3 times in one day and on the last visit adopted our precious dog Spunky. He had been treated for fleas 2 days earlier as well as almost every animal in the shelter. Well being 7 yrs old our daughter probably petted every animal there and on the way home with our new dog she showered him with kisses. The dog also slept with her and her older sister that night. 2 days later she complained of a headache and the next morning of nausea and feeling "shaky". Within an hour she had a seizure and had no history of seizures. She would not respond to us. We took her to the ER and she began having one seizure after another as well as vomiting and was eventually airlifted to another hospital. Our local doctor told us "it's bad!" She was in ICU for 2 days and spent 3 more days in the hospital. Prayers are the only thing that saved her. Our doctor could not believe she survived. I wish there were someway to get all these harmful poisons off the market. No telling what they are doing to our pets.
Dec 15, 2011 sandyart
My dog also passed away within 24 hours of administering flea and tick medication. She was a Jack Russell and was not even 2 years old. I have been administering the medication to my 3 dogs for 8 years and had no idea that it could cause death until this happened. I read the pamphlet and instructions what were included from beginning to end and NO WHERE does it say it could cause death. I hope that this helps save someone else heartbreak.
Jul 24, 2012 milo18
Can flea meds, (advantix), cause cardiac arrythmias in dog owner? My daughter became ill for 3 days after applying it to her dog. The dog became ill almost immediately, rapid shallow breathing, hyper, heartrate extremely fast. She scrubbed it off with dish detergent and started to have arryhmias within a couple of hours. They lasted 2 days and gradually dissappeared on the third day. She is a healthy 30 year old with no history of heart problems. Is this possible? Given the time frame of events, I believe it was the advantix.
Sep 1, 2012 katherine.storch.7
Now I'm angry! My dog has been sick for a couple days now ... lethargic, hiding, occassionally wimpering (he's eating and drinking now, but not 2 days ago) We couldn't figure out what the heck caused this sudden change of behavior in our normally happy pooch! We found him just over a year ago - dirty, hungry and uncared for. He gained weight and is the apple of our eye - we go everywhere together! Anyway, we recently found a flea on him even though we use AdvantixK9 so we decided to treat him to a Hartz Ultra Guard Flea & Tick shampoo. We did 3 baths in two weeks (pesky bugs!) Then this happened!! We tried to think what he could have gotten into to make him so sick ... and then ... BINGO! So here I am doing some research and read all of your posts and I'm floored! To think this crap shampoo (toxic chemicals) is the culprit of my dog's malaise. He's been hiding under the bed for 3 days now and only comes out when he needs to relieve himself - we have to carry him down the stairs because he has no energy! Yesterday and today he's eating again - I'm taking this as a positive sign - but the next time he comes out I'm getting him into the tub for a regular bath - just in case there is any residue still on his skin. I'm mortified that there is no real warning on the label as to what this sh*t can do to a dog!! aaarrggghhh - NEVER again!
Sep 5, 2012 AngelaxLove
you should all checkout Chemical free flea protection that lasts 2 years and is 100% safe.
Sep 9, 2012 maureenmc
You use food-grade Diatomaceous earth. It's a naturally occurring, soft, siliceous sedimentary rock available as a powder. Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. Food grade D-earth is a non-toxic way to kill fleas and worms. We've had flea problem recently and I didn't want to put extra Frontline on the dogs or change to Vectra(which is what the vets have been recommending). So I did my research and discovered food-grade Diatomaceous earth. Have I said food-grade? Because it HAS to be food-grade. I bought 3 pds on Amazon for $26. (Much cheaper in rural areas - buy it at the cattle feed store.) I've been sprinkling on their ped beds and on brushing it into their coats. It's been a couple days and the fleas are gone.
Jan 11, 2013 Hillbros
Does anyone know if applying Advantix as prescribed (down spine) can change the color of the coat? We have a beautiful 1 year old Weimaraner. The grey ghost had perfect coloring, but now he's dark grey on his back and spotty on hind quarters.
Feb 19, 2013 paperglyphs
My Jack Russell gets very ill after administering any flea or tick product. Before we knew that they all where doing it (shampoo, rinse topical -three different brands) the rinse almost killed her. She dry heaved for days and had the runs as well. I am really glad to hear about Flea Free. I hope I can get her to eat it.
Jun 28, 2013 wr1955
Pet Protectors - 96.67% effective, non toxic, protection for 4 years at a fraction of the price
Jul 6, 2013 HugoASt.
As I sit here reading all of these comments,(being a pet owner with 4 dogs all of which are very healthy and are treated with frontline plus) I realize that no one has given a whole lot of consideration to the comment left by the veterinarian. It seems that he out of all of us would know the most about this. I do not mean to sound as though I am putting anyone down I just wanted to say that we all should try and base our comments on fact based information. OF COURSE there warnings and side effects for ALL medications and we should all take precautions when using anything. However I think it is important to always consider the facts and not just base our understanding on a random comments from strangers. Do the research; I did and I knew that some of the information in this article was inaccurate as well, and I am not a vet. Some of us live in areas where the flea population is much higher and natural remedies are not as effective. The diseases and illnesses associated with fleas are a far greater risk that the possible side effects of the flea meds.
Jul 16, 2013 NotABot
HugoASt. While I do agree a vet is more knowledgeable, this particular one mentioned that s/he got all that information directly from those companies. Now, I don't know how you would run a company, but I'd be willing to wager that most would assure you their product isn't harmful if asked.
Jul 29, 2013 laceyf.
HugoASt: I completely agree that doing research on any topic is the most important thing. Where I very strongly disagree with you is when you talk about facts. The facts are not as clear as the 'vet tech' made them seem. And call me cynical, but I do not go to a multimillion dollar company to check the safety of their product, my trust does not stretch that far. The facts I have found is that most vets in my area have told me these medications are absolutely NOT safe and there are very real risks. I find it even more funny to hear that person say the medicine doesn't affect the central nervous system because I just checked my box of K9 Advantix II and it says directly the opposite. It literally says that it works with the central nervous system and in rare cases, it can severely poison dogs. I find a community of dog lovers and their experiences incredibly important, especially when it directly contradicts conventional medicine.
Jul 30, 2013 spunkymonkey
vet prescribed spot on ADVANTAGE. Within 24 hours my giant house rabbit was dead, my 2 dogs were poorly for days. Don't trust it if you love your pets.
Sep 19, 2013 brittanyrenee09
There has been issues with fleas in my area and I would like to apply flea and tick medication containing Phenothrin and Methoprene to my adult dog but I have a 10 week old puppy. Anyone know how long I should separate them to make sure my pup doesn't ingest any of it though play?
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