Is Frontline dangerous for dogs?


Frontline is probably one of the most widely available brands of spot-on for both cats and dogs for killing fleas and ticks sitting on your pets’ skin within a few hours.  However just recently I found out how dangerously Frontline may harm your pet.  So, let’s find out more about this.  The question of the day is this: is Frontline dangerous for dogs?


Why is Frontline top spot for dogs?

First of all, and before I go further into the subject, let me clarify that we have never used Frontline for our Indy.  Therefore I am unable to confirm whether Frontline may have an adverse reaction on our Border.

All vets will recommend that your pet, dog or cat, get a monthly spot-on treatment of flea and tick killer to prevent the pest from ‘nesting’ in your pet’s blood stream.  Generally speaking, most pet owners will opt for Frontline as this brand of pest killer is readily available in supermarkets, hence the price will be fairly affordable.Frontline

We have always used Advocate, which however we purchase directly from our vet under a care plan which also includes a tablet of Droncit to prevent worming, the annual booster inoculation, the vaccine against kennel cough and a free consultation.  For all of this we are charged £12 per month.  So, it’s difficult for me to work out how this compares to the average supermarket price of Frontline.

Amazon‘s price for Frontline goes between £10-18 per packet of 3 pipettes (one pipette per month) depending on your dog’s weight.


Frontline, dangerous for dogs?

The news came to me as a surprise, more so as in fact Frontline seems to be a very well established brand in pest immunisation provider for both cats and dogs.

It was my friends who alerted me that their cat started showing signs of unwell being two weeks after being subministered Frontline.  Shugar the she-cat stopped eating, started pulling her hair and started crawling.  To make a long story short, the vet had to refer her to a veterinary specialised hospital where Shugar was diagnosed with Hepatic Insufficiency – or, in lay terms. liver poisoning.

Shugar Health Scare

Shugar is now on her way to recovery, hopefully slow but sure.  Now, I am not an expert on cats, but if you know a little bit about dogs, you will know for a fact that liver poisoning in dogs can have lethal consequences – as it can with humans.

This news about Shugar led and encouraged me to browse more actively about Frontline.  Was this a one-off episode where poor Shugar had been unlucky?  Or was there a pattern of side effect for many pets whose owners had been using Frontline regularly on their cats and dogs?

The results, for once, left me speechless!

Consumer Affairs reviews on Frontline
Click on this image to find out alarming Frontline reviews left on Consumer Affairs website

All you have to do is google is ‘Is Frontline dangerous to dogs’, and you will be put before dozens of forums and reviews which unanimously condemn this product for its potentially life threatening side effects.

The results I came across record complaints of primarily skin issues, such as itchiness, redness, alopecia and other types of dermatitis, but they can extend to lethargy associated with severe vomiting.  I did not quite find evidence that Frontline can specifically cause liver conditions, but we all know that vomiting in dogs can lead to severe dehydration!


Frontline and its components – My research

I shall not go in the details of which ingredients and chemical components are used to make up Frontline or Frontline Plus.  You can discover that yourself when browing online.

My understanding, however, is that the manufacturers of Frontline are Merial, who also produce other medicinal drugs for pets to combat heartworm and to kill ticks and fleas.  The main components Merial uses in the manufacturing of Frontline is fipronil, which they introduced on the market in 1993 after it had been used in the late 1980s as potent broadly used insecticide.

Now, given the high volume of warning reviews readily available online, I have tried to find out directly from Frontline website what its ingredients are, or whether they have a safety warning.  I could not find such information.

I then decided to compare the information available on Frontline website with what’s available from Advocate website – and remember that Advocate is the spot-on we give our Indy, prescribed and sold by our vet practice.

I was firstly pleased to find out in order to access the Advocate website, you initially have to click a disclaimer to confirm that either you are a vet practice or that Advocate has been prescribed to your pet by your vet.

Also, once you access the Advocate pages, you find useful comparative information as to how effective the product is not only restrictively against fleas and ticks, but against any other type of larvae incubating in the upper epidermic layer of your dogs.

Advocate versus Frontline

Advocate is produced by Bayer, and its active component is imidacloprid, rated as moderately toxic by United States Environmental Protection Agency (EPA.  On the contrary, fipronil is classed by EPA as moderately to acutely hazardous pesticide.

I did not go into comparing the different country sites of Frontline.  However what I learned from one of the many reviews of Frontline products is that not only Frontline is not as effective as Advocate in keeping your dog (or cat) pest free, but that no side effect warning are published on its American website, with its British site only mentioning marginal side effects.

Admittedly, Advocate has an extensive FAQs page, but no warning of side effects either.  However, when searching for negative side effects from using Advocate on dogs or cats, I have only come across a handful, and none of them complained of anything more serious than itchiness and redness.


Most dangerous side effects of Frontline

Like with most, if not all, insect killers, when applied on the scruff of your dog’s neck Frontline can cause effects similar to the ones of dermatitis in humans, at different degrees of severity.

But where side effects were found to be scarier was when it was noticed that dogs that had just had Frontline applied on started showing signs of lethargy along with vomiting, which in some cases have lead to death.

Similar effects at times have been recorded in the dog owners, who equally started developing headaches, nausea and vomiting.

The other negative aspect that has been reported about Frontline is the fact that it does not seem to work as effectively as advertised in killing fleas from your dog’s coat.  Again, there have been many reviews to the fact that Frontline has not worked, and dog owners have ended up having to contact pest control services to remove the infestation from the whole house!


Frontline counterfeit

The final problem relating to choosing Frontline as a tick and flea killer for your dogs and cats, is the fact that, especially when purchased online, you may come across a counterfeit product, and not the genuine one manufactured by French Merial.

In other words, some Frontline products may actually be fake!  And like with all fake products readily available online, and sometimes regrettably in shops too, you are not going to get the components the product should contain, but you end up chucking in your pet’s blood stream only God knows what sort of poison.

That is the price sometimes you pay by opting out for a cheaper solution, rather than for a controlled drug prescribed solely by your vet.


What to use instead of Frontline

The way forward to all these issues issues is of course to go with a product which is prescribed and solely readily available from your vet surgery – such as Advocate, which we use for Indy.  Unless with other products I test and review on this website, I am unable to point you in the direction of where to purchase Advocate, as Advocate is not available from shops or supermarket.  Advocate is a prescribed spot-on.

But it’s not the only spot-on to be effective on your dog.  There are ever so many others.  The key is to speak to your vet, who will be able to advise you in the best interest of your dog.Goodby ticks naturally

Some vets prefer a more holistic approach, where they believe dogs, and cats, will naturally get rid of the pest in the same way as they used to when living in wilderness before they became tamed by humans.  But some more practical physicians do recognise the need for help in getting rid of the tiny bugs, and prefer to recommend naturally repelling oils.

I want to show you here one of the many recipes I found on Dogs Naturally to get rid of ticks purely by using essential extracts:

Once again Amazon comes to the rescue with quite a few products which I have not tried on Indy, but which are all chemicals free and contains purely natural vegetal extracts.  Have a look for yourself by clicking here.  But be careful – as you can see, even Amazon throws Frontline in the mix of natural remedies!


I am never going to use Frontline on Indy

Yes, you guessed correctly.  I am never going to use Frontline for my Indy for two main reasons: we have no complaint with what our vet has prescribed to Indy in all this years; but also, why would I want to experiment on my dog a product that may cause him to be unwell?

Don’t get me wrong, I am not suggesting that Frontline will definitely have an ill effect on your dog.  Like with all canine products, as well as human, some adverse reactions are down to the particular constitution of your dog and to his or her skin and metabolic sensitivity.

Nevertheless, given the fact that so much else is available both naturally or directly through your vet surgery, I do no recommend that you try out Frontline purely to check your dog’s level of tolerance to this product.  Don’t gamble with your dog’s health – go safe!!!

Always apply your spot on on the scruff of your dogs neck



  1. // Reply

    Your website is very informative. I had no idea that Frontline was dangerous. It shouldn’t surprise me though, if we are to be careful with the chemicals we put onto our own bodies, foreign substances on animals should be the same. Thanks for sharing and good luck!

    1. // Reply

      Yes, that’s true Cristy. I for once am not all for natural at all costs – I do believe that chemically based drugs are necessary in specific instances. But in this time and age, when so much information is available online, it’s silly for us dog owners not to take advantage by going through reviews. What prompted me to write about it is the amount of negative reviews. Alarming and scary!!

  2. // Reply

    My children have been nagging me for a dog for a while now but that’s one thing that bothers me about them, the fleas!
    I’m not saying all dogs have them but I don’t think I would like the thought that they might catch them one day. I have bookmarked this post for future reference just in case my children persuade me and I will have at least a starting guide as to what to use and what not to use if the dog ever gets riddled with them, thanks

    1. // Reply

      Would you believe me, Matthew, if I told you that not once in the 7 years we’ve had our Indy have we had fleas in our house ever! The key is to treat your dog every month religiously. And that’s the advantage of going with a pet care plan with your vet: you end up paying possibly the same for a trusted product as if you bought an over the counter not controlled drug, and you avoid forgetting to treat your dog. With regular spot-on treatment you’ll be flea and tick free (as well as other parasite bugs) for good!

  3. // Reply

    It so scary when I thought front line was a trusted product for my dog.

    I’m definitely moving to a more natural alternative as you recommended.

    Thanks for sharing Gulia

    1. // Reply

      Or, you may want to discuss options with your vet, Vince. I believe, with current legislation, gone are the days of cowboy vets who just sell you the product for their benefit. Your vet would have your dog’s medical history and certainly will have your dog’s best interests at heart.

  4. // Reply

    Oh my! I have used Frontline on my cat before only once in the past. But I thought it was too expensive so I switched to Pet Armor. Pet Armor works great and my cat has never had a reaction to it. I’m so glad I’ve found your articles as I was never aware of these deadly side effects of Frontline. I will tell my friends and family about this product. Very helpful article! Thanks for sharing. Btw your dog is so cute 🙂

    1. // Reply

      Thank you ever so much, my Indy know even too well what a cutester he is, and even now in his old age he takes full advantage of his endearing features. He’s got us wrapped round his pinky paw 😇
      I’m glad you appreciated my review, Tee. I’m not aware of Pet Armor, but I’m glad to hear it’s working for your cat. The advantage many see with Frontline is that it’s readily available online and in shops or supermarkets. The disadvantage is that your vet cannot monitor if you are regularly treating your pet, and whether the product is genuine and harmless. But unfortunately, given the widely spread availability, side effects have become more resounding and less contained. A real shame for the manufacturers, but yes, I would mention this to your family, just to be on the safe side.

  5. // Reply

    So much involved with this, I had absolutely no idea. Frontline is definitely a well-trusted brand and very popular, to say the least. However, the “life threatening” side effects make me want to try a better alternative. I’ll take your advice on board and go for a product prescribed to my pet by a vet. Thanks a lot!

    1. // Reply

      You may want to try the holistic approach too, but that’s up to you, Brandon. But yes, I believe consulting with your vet is the best option. Let us know how you get on 🤗

  6. // Reply

    Hi Giulia. I don’t have a dog in my house but my sister is an animal husbandry and she loves taking care of her two dogs. I will send her this precious information. Thank you.

  7. // Reply

    Good evening Giulia,

    I fully agree with you not to use Frontline on Indy. It is a pesticide after all.
    In human food, we also find so many bad things like GMO, Chemicals, Additives, and more of these niceties. The more natural products we use the better and this is valid for us as well as for our pets.

    Regards, Taetske

    1. // Reply

      I’m not an all natural type of person, Taetske, as I believe we need to expose our immune system in order for it to grow stronger and more resistant to viruses. But I’m not sure the same can be applied to pets, more so when we are talking about strong pesticides. As mentioned, I’m not necessarily saying Frontline is going to have a negative impact on all pets, but, given the bad press, I wouldn’t want to risk it.

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