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PetArmor Plus vs Frontline Plus Flea Treatment: The Differences (Vet Answer)

Written by: Dr. Rebecca MacMillan MRCVS (Veterinarian)

Last Updated on April 9, 2024 by Dogster Team

PetArmor Plus vs Frontline Plus Flea Treatment

PetArmor Plus vs Frontline Plus Flea Treatment: The Differences (Vet Answer)


Dr. Rebecca MacMillan  Photo


Dr. Rebecca MacMillan

MRCVS (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Fleas are the number one parasite that veterinarians see in practice. The most common type of flea is Ctenocephalides felis (the cat flea) which can infect cats, dogs, and rabbits as well as biting humans too, causing itchiness but also transmitting disease. An adult flea is brownish-red in color, wingless, and approximately 1-3mm in size. Mating fleas will introduce eggs into our homes with infestations occurring quickly.

Ticks are also a big concern for our pets. These larger parasites latch on and feed on an animal’s blood, which in itself is unpleasant, but they can also cause nasty infections with the bacteria they contain in their mouths. Like fleas, they can also lay eggs that fall off into our homes.

We all want to keep our pets parasite free, but with an array of different anti-flea and tick products available it is easy to get confused! In this article, we look at the differences between two of those products, PetArmor Plus and Frontline Plus, and dig a bit deeper into the potential pros and cons of each one.

Overview of PetArmor Plus

PetArmor Plus for Dogs

PetArmor Plus is a product that is effective against fleas, flea eggs, flea larvae, ticks, and chewing lice. It comes as a liquid medication in small individual pipettes that need to be applied to the skin on the back of the dog. They are available to buy in packs of 3, 6, or even 12 from some retailers. It lasts up to 30 days when applied, so monthly reapplication is advised to prevent any reinfestations.

The product contains 9.8% fipronil and 8.8% (S)-methoprene as its active ingredients. Fipronil is an insecticide that kills adult fleas by disrupting their nervous system. (S)-methoprene is a growth regulator and stops the development of the immature stages of the flea life cycle (the eggs and the larvae). Regular PetArmor doesn’t contain (S)-methoprene, so ensure it is PetArmor Plus that you purchase if you want this more complete coverage.

PetArmor Plus is an effective product at both killing current flea infestations and preventing future infestations. PetArmor Plus states on their website that fleas on your pet are killed within 24–48 hours after application.

Applying the Product

You will need to purchase the right size for your dog, so you must weigh your dog accurately. It is important not to split doses between dogs and to buy the correct size of product for each dog. It is available to buy in the following different weight brackets: Small 5-22 lbs, Medium 23-44 lbs, Large 45-88 lbs, and X-large 89-132 lbs. If you accidentally underdose your dog its effectiveness could be reduced, leading to product failure.

To apply PetArmor Plus you will need to open the pipette as instructed by the product packaging, part the fur on the back of your dog’s neck, and apply all of the liquid contents. In larger dog’s you may need to apply the liquid in 3 or 4 different areas down the dog’s back.

The product doesn’t require a veterinary prescription to obtain it, so it can be purchased in pet stores and via online retailers. It is safe to use in puppies from 8 weeks of age onwards.

woman hand applies Dog Flea Tick Drops to the skin of a cute red mixed breed dog
Image By: Dmitriev Mikhail, Shutterstock


The dog version of this product should not be used in cats and the manufacturers advise keeping cats away from treated dogs for 24-48 hours after application in case any accidental contact and ingestion occurs. A cat version is available to buy which contains a lower concentration of (S)-methoprene.

The product isn’t effective for pets suffering from certain types of mites, nor does it offer protection against internal parasites like worms, so you will need to speak to your veterinarian if you wish to look at other parasite products that cover these.

  • Contains (S)-methoprene which helps kill off immature fleas in the environment as well as fipronil for the adult fleas
  • Doesn’t require a veterinary prescription so can be easily obtained
  • A variety of different sizes available for different sized dogs
  • Effective against ticks and chewing lice as well as fleas
  • Need to be careful when using around cats
  • Claims to start killing fleas and ticks within 24 hours but could take up to 48 hours, so can take a little while

The PetArmor website details more information about the product.

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Overview of Frontline Plus

Frontline Plus Flea and Tick Treatment for Dogs

Frontline plus claims to be a veterinarian-recommended flea and tick treatment, and they use this in a lot of their marketing. The product seems to cost more, however it contains exactly the same active ingredients as PetArmor Plus: the insecticide fipronil at 9.8% concentration and the insect growth regulator (S)-methoprene at 8.8%. It is also effective against the immature stages of the flea life cycle and chewing lice.

Fipronil is a phenylpyrazole insecticide that blocks GABA-gated chloride and glutamate-gated chloride (GluCl) channels in the flea. These control cell excitability and things such as movement and feeding. This disruption causes damage to the flea’s nerve and muscle control resulting in death.

The (S)-methoprene component targets other stages of the flea life cycle, meaning that a flea infestation can be brought under control more quickly. Flea eggs are disrupted from hatching and larval growth is affected.

Regular Frontline contains only fipronil, so make sure you are purchasing Frontline Plus if you are wanting the additional benefits that the (S)-methoprene provides.

The product is said to start killing fleas within 4 hours of application and claims to cause death to all of the adult fleas on your pet within 12 hours. It will also cause ticks to die and start falling off during this time frame too. This is quicker than PetArmor Plus says on their website, though it is unclear why the timeframe is different between the two products that contain the same active ingredients.

Applying the Product

Frontline Plus is available to purchase for the following weights of dog: 5-22 lbs, 23-44lbs, 45-88lbs, and 89-132 lbs. You can purchase it in packs of 3, 6, or 8 doses. You should not split individual doses between dogs, you should buy the correct product for the dog of that size and use one pipette per dog. Frontline Plus is safe to use in puppies 8 weeks of age and older.

The application of the product is similar to PetArmor Plus. Open the pipette as per packet guidelines, apply the liquid contents to the skin on the back of the dog’s neck (parting the fur to allow access to the skin itself). Larger dogs may need the liquid applied in 3 or 4 spots down the dog’s spine.

It is advised to apply the product monthly to ensure adequate tick protection, though flea protection lasts a bit longer than this. Monthly is also advised for full flea protection when reinfestation is highly likely.

woman hand applies Dog Flea Tick Drops to the skin of a cute red mixed breed dog
Image By: Dmitriev Mikhail, Shutterstock


The same contraindication applies to Frontline Plus as to PetArmor Plus – do not apply the dog product to cats and seek veterinary advice for protection from other parasites.

  • Contains (S)-methoprene which helps kill off immature fleas in the environment
  • Doesn’t require a veterinary prescription so can be easily obtained
  • A variety of different sizes available for different sized dogs
  • Effective against ticks and chewing lice as well as fleas
  • Claims to start killing fleas within 4 hours, with all adult fleas on the dog dead in 12 hours
  • Need to be careful when using around cats
  • Prices seem to be more expensive for Frontline Plus than PetArmor Plus

The Frontline Plus website has more information about their products.

Which One Should You Use?

As you have probably gathered, both PetArmor Plus and Frontline Plus are very similar products relying on the same active ingredients and same methods of application.

The following table summarizes the key comparisons:

  PetArmor Plus Frontline Plus
Parasites Flea, flea eggs, flea, larvae, ticks, and chewing lice Flea, flea eggs, flea, larvae, ticks, and chewing lice
Formulation A topical liquid A topical liquid
Active ingredients Fipronil and (S)-methoprene Fipronil and (S)-methoprene
Starts killing fleas… Within 24 hours Within 4 hours
Frequency of application Monthly Monthly
Prescription required No No
Care around cats Yes Yes
Cost Often cheaper than Frontline Plus Often more expensive than PetArmor Plus
Pack sizes 3, 6, or 12 dose packs 3, 6, or 8 dose packs

From the table, you should be able to see that the two products are much the same. One of the differences seems to be the time it takes to kill fleas. Frontline Plus states on their website that their product is effective in killing all adult fleas within 12 hours, whereas PetArmor Plus suggests it takes between 24 and 48 hours for their product to be effective. It’s not clear why this is different given that the products contain the same active ingredients in the same amounts.

The only minor differences between the two are that it is possible to get slightly different pack sizes, and their cost. It seems that Frontline Plus is often more expensive to purchase than PetArmor Plus, so this may be a factor in your decision making. 

veterinarian, assisted with a vet nurse, applying a spot-on antiparasite drug to the skin on the neck of a dog
Image By: Pongpreecha Malaluang, Shutterstock

Flea Life Cycle Considerations

With both products, it is worth noting that you may still see fleas in your home for a little while after application. This is because any flea eggs that were laid before the flea treatment was applied may still be hatching out of the environment. A flea infestation in the home can be tricky and take time to get on top of. Ensuring your pet has his parasite product applied regularly as instructed will kill any fleas on them and prevent further flea reproduction from occurring. You should also make sure all in-contact pets have been treated with appropriate parasite products.

To treat the home, you can use chemical sprays to kill eggs and larvae, but not many products will touch the resistant pupal cocoon, so this will require patience. As they all eventually hatch out and hop onto your pet, they will then come into contact with the parasite product and die (but this process could take several weeks). You can speed things up by increasing the temperature and humidity in your home (damp towels on radiators and boiling kettles in rooms), hot washing bedding, and lots of vacuuming as the vibrations help cause hatching to occur faster.

Fleas can also seem livelier than normal following the application of PetArmor Plus or Frontline Plus. This is due to the effect the fipronil is having on the fleas’ central nervous system, which makes them hyperexcitable and extra active before they die. This is just a sign that the product is working. 

Other Suggestions

When deciding on a flea product for your pet, you may decide that a tablet is easier to administer to your dog than a topical liquid spot-on. Some dogs with sensitive skin can also have local reactions to spot-on products. If this is the case with your dog, then it would be worth speaking to your veterinarian about some of the alternative treatments available. There are also some effective flea and tick collars which they may be able to suggest too, so don’t feel limited to spot-on alone.

Your veterinarian will also be able to help assist you if your dog is suffering from excessive itchiness from his flea problem, as some dogs can have flea allergies. If your dog’s skin is sore or scabby or he is constantly scratching, give them a call.

Dogster_Website dividers_v1_Jan 18 2024-03


Ultimately there are minimal differences between PetArmor Plus and Frontline Plus other than their branding and packaging. Both products contain the same active ingredients and should therefore be just as effective as each other. In terms of how long does it lasts, each product advises a monthly application. Which one you buy may depend on the availability at your local store, or cost could be the primary factor for you when choosing. Whichever product you decide on, make sure you use the correct dose for your dog and follow the packet instructions to ensure optimal effectiveness.

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