In Fipronil For Dogs, Sarah Holloway investigates this common insecticide and answers your questions about using fipronil on your Lab.
Protecting your dog from flea and tick bites is a must for any Labrador owner.
And it’s highly likely that if you’ve ever researched different flea and tick treatments, you’ve already come across the chemical name fipronil. In this article we explain what fipronil is, discuss whether it’s right for your Labrador, and find out how to use it correctly.
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What is fipronil?
Firpronil is an insecticide which kills the fleas and ticks that try to bite our dogs. Fleas and ticks are parasites that consume the blood of host animals. Not only can their bites be itchy and uncomfortable, they can cause painful allergic reactions or transmit dangerous illnesses. So we protect our dogs from bites by using a regular flea and tick prevention treatment.
Fipronil is the active ingredient in the flea and tick treatments Frontline, Sentry Fiproguard, PetArmor, and Hartz First Defense. Fipronil also kills ants, beetles, cockroaches, ticks, termites, weevils and other insects, so it is also widely used in other industries, such as agriculture and pest control.
Where did fipronil come from?
Fipronil is one of the most longstanding weapons in our pet flea-control armoury. Developed by the French pharmaceutical company Rhône-Poulenc in the 1980s, fipronil was first marketed for treating fleas on dogs in the US by Frontline in 1996. Because fipronil is widely sold for controlling other household pests too (it’s the main ingredient in Termidor for example), I’m going to stress the obvious now: only ever use a fipronil product designed for dogs on your dog.
How effective is fipronil for dogs?
Fipronil is highly efficient at killing fleas and ticks on your dog.
Fipronil-containing products (usually Frontline or Frontline Plus*) have been included in many effectiveness studies over the years. They consistently kill over 90% of fleas and ticks on the dogs taking part, and keep them flea and tick free for at least four weeks. There are some public concerns about resistance, and we’ll look at those below
What conditions is fipronil used to treat?
Fipronil for dogs kills adult fleas and ticks on your Labrador, whether they have already bitten him, were waiting in his fur when you applied the treatment, or if they hop onboard in between treatments. The Frontline Plus range, which contains fipronil and S-methoprene, also prevents flea larvae maturing into adult fleas.
Fipronil does not treat flea- or tick-borne diseases, but there is some early evidence to suggest that fipronil can inhibit the transmission of Lyme disease and canine ehrlicosis from tick to dog in the first place (it’s not understood how yet).
Your vet might also prescribe a fipronil product such as Frontline to treat ear mites in dogs, although they seem to be falling out of favor these days to other, faster-acting products. Finally, fipronil products will treat chewing lice infestations in dogs.
What forms does fipronil for dogs come in?
Fipronil spot-on for dogs
Spot-on treatments are pre-measured doses in single use pipettes, which you empty onto the back of your dog’s neck. Different doses are available, and you choose the correct one based on the weight of your Lab. Even the biggest dose, for dogs over 40kg, is less than a teaspoon. It’s important to get the dose right, so your veterinarian will weigh your dog before prescribing the appropriate product
Fipronil spray for dogs
Sprays* on the other hand come in a single concentration, and you calculate how much to apply based on the weight of your lab and the instructions on the bottle.
Usually the correct dosage means saturating your dog’s coat, and for this reason spot-on treatments are much more popular, because they are quicker and less messy. Fipronil spray does have the advantage occasionally however. For example if you have several animals of different sizes and want to buy one product rather than several separate products. As we shall see a bit later, it also appears to bring fewer unwanted side effects.
How does fipronil work?
Have you ever wondered how a tiny pipette of flea treatment applied to the back of your Labrador’s neck can protect their whole body from fleas for an entire month? And how such a small dose of anything can kill so many fleas?
Well, here are some answers. For a start, only about one tenth of that tiny Frontline pipette contains fipronil. (Just think how potent an insecticide that makes it!) The rest of the contents are inert oils to help the fipronil spread across the surface of your dogs skin. As it spreads, it gravitates to the hair follicles and sebaceous glands. The fipronil solution sinks into the sebaceous glands and forms tiny reservoirs there. So the amount of the fipronil on the surface of the skin constantly replenishes whenever the glands secrete sebum. So that’s how it goes on working for a month, even after your dog has had a bath or swim.
When an insect comes into contact with fipronil, it acts on their central nervous system by triggering all the nerve endings to act constantly. This overwhelms their nervous system with signals and causes it to fail, ultimately killing them. Only tiny amounts of fipronil are required because it acts on an incredibly minute molecular level, and flea and tick’s nervous systems are not big.
Is fipronil right for your dog?
Fipronil based products for treating fleas and ticks have had a huge stake in the market for decades now. The only way to be sure you’re choosing the right flea and tick control treatment for your Labrador is by consulting your veterinarian when you choose it.
They will consider your pet’s full medical history, and discuss your preferences (for example whether you’re more comfortable administering a spot on treatment or an oral treatment) before making a recommendation. They will also take into consideration other pets living at home, since some treatments are particularly toxic to other species. Fipronil is highly toxic to fish, for example.
You might find that settling on the right treatment for you is a matter of trial and error. Unfortunately there is not a handy list of criteria that guarantees fipronil (or any other flea treatment) is the best for you!
Can I buy fipronil over the counter?
In some regions, Fipronil tick and fleas treatments can’t be sold over the counter without a prescription. Some websites also require a prescription, although others don’t. If you’ve never used fipronil for dogs before, always consult your veterinarian before using it for the first time, and get a prescription.
Alternatives to fipronil
Fipronil is a slow acting insecticide, which means it takes up to 48 hours to kill the fleas and ticks on your Labrador. In other settings, being slow acting is an advantage. For example when used to treat ants or cockroaches in the home. It gives a chance for treated insects to get back to the nest, where they poison others too.
However, when it comes to treating fleas and ticks on our dogs, fipronil might be losing its edge to other faster-acting treatments. CAPSTAR* and K9 Advantix* spot on treatments both outperformed Frontline over three hour and eight periods in a 2005 study.
Some newer products also protect against re-infestation for longer. This is important because most of the time when flea treatment fails, it’s because it hasn’t been re-administered promptly when it was due. Bravecto oral treatments successfully prevented re-infestation for three months in a 2014 trial.
What about resistance to fipronil?
It is quite common to hear dog owners and their veterinarians commenting that fleas may be becoming resistant to fipronil. Resistance means that the target of the insecticide – in this case the fleas on your dog – is becoming less susceptible to its toxic effects. If fleas are becoming resistance to Fipronil then this would result in the product failing to kill the fleas that it come into contact with.
However, product failure can be caused by factors other than resistance. And it is sometimes difficult to disentangle these – especially under home conditions. Resistance – or lack of it – can be tested under laboratory conditions. And a recent study published in 2016 found that no significant reduction in the susceptibility of fleas to fipronil The study concludes that the failure of the product may be due to “operational factors such as failure to adequately treat the pet and follow label directions”.
If you’re using a fipronil product at the moment but you’re not completely happy with it, check that you are following the instructions correctly, then ask your vet if another treatment would be more suitable for you.
When not to use fipronil
Fipronil-based products are not suitable for puppies under eight weeks old or dogs weighing less than 2kg. Bear in mind this might preclude many toy dogs for their entire lifetime. If your Labrador has a much smaller canine companion living at home too, your vet will help you choose an appropriate way to protect them from ticks and fleas too.
How to use fipronil for dogs
Always use fipronil products in accordance with the instructions included in the packet. If you mislay the instructions, try looking on the manufacturers website. For example the instructions for Frontline together with other frequently asked questions are here on their website. Wait until the application site is dry before petting your dog again.
Researchers at Murray State University found that low concentrations of Frontline are transferred to owners’ hands after five minutes of petting for up to four weeks after treatment. The quantities are far too low to ever cause harm to the average dog owner, but it’s a sage reminder to wash your hands after petting your dog, and make sure kids wash theirs.
Don’t bathe your Lab or let them go swimming for two days after treatment. Remember that if you are raising your Lab from a pup, you’ll need to keep track of their weight to make sure you’re giving the correct dose each time.
Side effects of fipronil and when to report them
Fipronil has very low toxicity to dogs, humans and other mammals, so adverse reactions are rare. A review of side effects reported in Australia between 1996 and 2003 found that the most common side effect of using fipronil for dogs was skin irritation or hair loss at the application site. They also found that spot on treatments were occasionally linked to stomach upsets (especially if pets were able to get hold of and chew the pipette) and neurological problems including lethargy, lack of appetite and excess drooling.
Interestingly, no cases were recorded of spray treatments causing stomach upsets or neurological problems. However that’s not to say that they aren’t possible, and the writers stressed to importance of not shutting a freshly sprayed pet in a confined space, due to the risk of inhaling fumes.
Consult vet if you are ever worried about side effects from using a flea or tick treatment. If they ask you to go in for an examination, take the packaging of the product you have been using.
Fipronil for dogs – a summary
Flea and tick treatments based on fipronil have been keeping our pets healthy for generations. They are very safe, and as long as you remember to re-administer them on time, they are very reliable too.
In recent years new products have reached the market which are faster acting, easier to administer, and provide longer protection. So maybe we will start to see pet owners moving away from fipronil in the future. But it’s not going anywhere soon.
How about you?
Do you use fipronil products for your Lab? Have you tried them, but decided you prefer something else? Share your experiences in the comments section below.
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Affiliate link disclosure: Links in this article marked with an * are affiliate links, and we may receive a small commission if you purchase these products. However, we selected them for inclusion independently, and all of the views expressed in this article are our own.
Australian Pesticides and Veterinary Medicines Authority, “Safety of Fipronil in Dogs and Cats: a review of the literature”.
Coles, T. B. & Dryden, M. W., (2014), “Insecticide/acaride resistance in fleas and ticks infesting dogs and cats”, Parasites and Vectors, 7:8.
Jackson, D. et al, (2009), “Fipronil Technical Fact Sheet”, National Pesticide Information Center, Oregon State University Extension Services.
Jennings, K. A. et al, (2002), “Human exposure to fipronil from dogs treated with frontline”, Veterinary and Human Toxicology, 44(5):301-303.
Otranto, D. et al, (2005), “Efficacy of a combination of imidacloprid 10%/permethrin 50% versus fipronil 10%/(s)-methoprene 12%, against ticks in naturally infected dogs”, Veterinary Parasitology, 130(3-4):293-304.
Rohdich, N. et al, (2014), “A randomized, blinded, controlled and multi-centered field study comparing the efficacy and safety of Bravecto™ (fluralaner) against Frontline™ (fipronil) in flea- and tick-infested dogs”, Parasites and Vectors, 7:83
Schenker, R. et al, (2003), “Comparative speed of kill between nitenpyram, fipronil, imidocloprid, selamectin and cythioate against adult Ctenocephalides felis (Bouché) on cats and dogs”, Veterinary Parasitology, 112(3):249-254.
Kidd, L. & Breitschwerdt, E. B., (2003), “Transmission Times and Prevention of Tick-Borne Diseases in Dogs, Companion, 25(10): 742-751
Rust, M. “Insecticide resistance in fleas” Insects Mar 2016
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