Comfortis vs. NexGard: Which Flea Treatment is Better?

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Even though I spend a great deal of time researching everything I can about dogs, like behavior, foods, and medications, I am always finding new products.

Recently I discovered Comfortis, an effective flea product.

Because Comfortis appeared to be similar to NexGard, I thought it would be worth comparing the two side by side.

In this article, Comfortis vs NexGard, I will dive into how these products work, their pros and cons, and which situations are best suited for each product.

For those looking for a quick answer: NexGard is my initial pick for a flea and tick product since it is effective against more parasites than Comfortis.


  • Active Ingredients: Spinosad
  • Type: Flavored Tablet
  • Duration: 1 Month

Comfortis is an Elanco Animal Health Incorporated company[1]. Elanco, an American pharmaceutical company, was founded in 1954.

Comfortis’ active ingredient is spinosad, which is in the spinosyn chemical family.

Chemicals in the spinosyn family are made up of two fermented compounds that have been proven as an effective insecticide, often used in fields.

Comfortis is a beef-flavored tablet that contains pork instead of beef, making it ideal for dogs with severe food allergies.

Comfortis lasts a full month, and it is easy to give because it’s palatability.

Comfortis is effective at killing fleas quickly; in just 30-minutes, Comfortis starts going to work. And within four hours, Comfortis will eliminate all adult fleas.

For active flea infestations, it is recommended you use Comfortis for three months.

Comfortis is effective against adult fleas but not against eggs or larvae.

However, over the next months, it will continue to kill adult fleas, and in three months, the fleas will be fully eliminated.

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After all the fleas have been killed, you should continue to use Comfortis to prevent future flea infestations.

Comfortis is safe to use on puppies 14-weeks and older.

Read Also: Capstar vs Comfortis


  • Starts killing fleas in thirty minutes
  • Chewable tablets are easy to administer
  • Does not contain beef
  • Safe for puppies 14-weeks and older


  • Does not kill other parasites
  • Interacts with ivermectin

To start killing fleas fast with Comfortis, click here!


  • Active Ingredients: Afoxolaner
  • Type: Chewable Tablet
  • Duration: 1 Month

NexGard is made by Boehringer Ingelheim & Merial Group pet products.

Boehringer Ingelheim Group is a family-owned company that focuses on improving both animal and humans’ quality of life.

NexGard is a beef-flavored chewable tablet that is easy to give and lasts thirty-days.

NexGard is useful at eliminating fleas and ticks and killing three types of mites:

  • Sarcoptes mites, which cause sarcoptic mange[2]
  • Demodex mites, which cause demodectic mange
  • Otodectes mites, or ear mites

NexGard kills four varieties of ticks, including Black-legged ticks, American dog ticks, Lone Star ticks, and Brown dog ticks.

NexGard starts killing fleas in only four hours, including all life stages disrupting the life cycle.

NexGard is safe for puppies eight weeks old and older.

Afoxolaner is the primary ingredient in NexGard, which is a powerful parasiticide.

Afoxolaner attacks the insect’s nervous system, resulting in uncontrolled overstimulation, eventually killing the parasite. The pesticide has been created to impact insects only and should not affect dogs.

The Afoxolaner spreads across the dog’s body, so when a tick, flea, or mite bites them, the parasite will die.

Unfortunately, Afoxolaner needs insects to bite the dog and does not work as a preventative.

Afoxolaner is part of the isoxazoline chemical group.

The disadvantage of employing products in the isoxazoline family is that they can increase the risk of seizure activity in dogs who suffer from epilepsy and can bring about seizures in dogs with no seizure history.

Related: Nexgard vs Nexgard Spectra: Which Should You Use on Your Dog?


  • Is effective against three types of mites
  • Works to kill four varieties of ticks
  • Waterproof
  • Safe for puppies eight weeks old and older


  • Does not work as a preventative
  • Parasites need to bite the dog to be effective

To order NexGard today click here!

For more information, check out our full NexGard review!

Comfortis vs NexGard Compared

Kills Fleas and TicksYesFleas Only
Repels Fleas and TicksNoNo
Other Parasites3 Types of MitesNo
Active IngredientAfoxolanerSpinosad
Duration1 Month1 Month
Prescription NeededYesYes
Waterproof or Water ResistantWaterproofWaterproof
Price per Month (Based on a Small Sized Dog)$19.66$16.16
Minimum Age Requirement8-weeks14-weeks

Side Effects


  • Vomiting
  • Depression
  • Lethargy
  • Decreased appetite
  • Incoordination
  • Diarrhea
  • Itching
  • Trembling
  • Excessive salivation
  • Seizures

Also, using ivermectin, commonly used to prevent or treat heartworms, internal worms, and mites, with Comfortis may increase the risk of additional side effects, including[3]:

  • Trembling and twitching
  • Salivation and drooling
  • Seizures
  • Incoordination
  • Excessive dilation of pupils
  • Blindness
  • Disorientation


  • Seizures
  • Vomiting
  • Diarrhea
  • Loss of appetite
  • Itching
  • Lethargy
Comfortis NexGard easy to give chewable flea control meds
Both Comfortis and NexGard are beef-flavored chews your dog may mistake for a treat!

Which Flea Treatment is Better?

Which is Safest?

Winner: NexGard

NexGard has side effects, though it does not have adverse drug interactions with ivermectin, commonly found in heartworm preventatives.

Additionally, NexGard has fewer possible side effects than Comfortis.

Which Works Fastest?

Winner: Comfortis

Comfortis starts killing fleas in just thirty minutes and kills 100% of adult fleas within four hours.

Which is the Cheapest?

Winner: Comfortis

Based on the pricing for small breeds, Comfortis is a few dollars less per month.

Which Lasts Longer?

Winner: Tie

Both products last for thirty days.

Standout Features

Comfortis kills fleas faster than most flea products, making it ideal for those combatting a current flea infestation.

NexGard works to eliminate three types of mites and four types of ticks.

Overall Winner

Winner: NexGard

Though NexGard is a bit more expensive than Comfortis, it works against more parasites than Comfortis.

Additionally, it is safe for younger puppies and has fewer side effects.


Comfortis and NexGard are both fast-acting effective products against fleas and last a full thirty days.

Even though NexGard is my preferred choice between the two, there are times when Comfortis may be the better option.

For example:

  • If your dog has a severe flea infestation, Comfortis is best to get rid of fleas fast.
  • If you have a current infestation and a multi-pet household, Comfortis might be the best choice to help prevent the spread of fleas.
  • If you have a younger dog then NexGard is the best choice.
  • If you are looking for a preventative against ticks, NexGard is the best option


Can You Use Comfortis and NexGard together?

Though they both use different active ingredients, it should not be necessary to use multiple flea preventatives.

Is it Safe to Use Comfortis and Heartgard Together?

It is not recommended to use products containing ivermectin with Comfortis, so you should not use Heartgard and Comfortis together.


Comfortis vs Nexgard Flea Medications for Dogs Pinterest

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