Comfortis Flea Preventative
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At a Glance
First FDA-approved monthly chewable flea preventative.
#1 veterinarian-recommended prescription flea-only medicine
Its active ingredient spinosad works to paralyze and eventually kill fleas.
Starts killing fleas after 30 minutes once administered.
Continues working on your pets for the next 30 days.

Comfortis Flea Preventative

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At a Glance
First FDA-approved monthly chewable flea preventative.
#1 veterinarian-recommended prescription flea-only medicine
Its active ingredient spinosad works to paralyze and eventually kill fleas.
Starts killing fleas after 30 minutes once administered.
Continues working on your pets for the next 30 days.

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Total Price

Elanco Animal Health Logo

Ultimate Guide to Comfortis

Meet the First Chewable Flea Killer: Comfortis!

Comfortis is the first oral veterinarian-approved and FDA-approved flea preventative for dogs AND cats. The beef-flavored chewable starts killing fleas 30 minutes after ingesting. Comfortis ensures that your pet is in the best lovable condition comfortably.

How does Comfortis work?

Comfortis is a flea medicine with one active ingredient, the well-known insecticide Spinosad. Spinosad is an effective natural substance known to cause flea paralysis once the blood-sucking parasite is exposed to their nervous system and then effectively kills them before they lay eggs. A pet owner will see the fleas will fall off of their beloved pets beginning 30 minutes after pilling.

How is Comfortis administered?

Comfortis is administered orally once a month and protects your pet for the next 30 days. These beef-flavored chews are highly recommended to be ingested in a meal for maximum effectiveness. Comfortis is used year-round for maximum effectiveness.

Body Weight of Dog (D) or Cat (C) Spinosad per Tablet (mg) No. of Tablet(s)
D 5 - 10 lbs. C 4 - 6 lbs.140 (Pink)One
D 10.1 - 20 lbs. C 6 - 12 lbs.270 (Orange)One
D 20.1 - 40 lbs. C 12 - 24 lbs.560 (Teal)One
40.1 - 60 lbs.810 (Blue)One
60.1 - 120 lbs.1620 (Brown)One

Pet owners especially love that they and their family can play with or touch their pets after treatment, pets can play or get wet (e.g., bathe or swimming) after pilling, and there is no mess or stain on cloth as commonly seen from topical solutions.

What are the potential side effects of which you should be aware?

Your dog might most likely experience vomiting after ingesting Comfortis's chew! If vomited within the first hour, your dog must ingest another full dosage.

Other possible reactions can be diarrhea, depression, incoordination, and decreased appetite.

Comfortis can be taken simultaneously with heartworm prevention products or other intestinal parasite preventatives. Intense itching can cause a pet to ingest a flea while scratching or chewing their skin or coat, which may cause tapeworm infestation.

Frequently Asked Questions
  1. Can I get Comfortis without a vet prescription?

    Unfortunately not. Pet medications need prescriptions. If your dog or cat has fleas, you need the brand Comfortis, or generic medical name spinosad. When it comes to eliminating fleas on your dog or cat, you want a flea medicine you can trust.

  2. Is there a difference between Comfortis for dogs and for cats?

    They work the same for dogs and for cats. Cats can be a little more finicky when it comes to giving them their monthly flea medicine. In controlled laboratory studies, Comfortis kills 100% of fleas on dogs and 98% of fleas on cats after four hours.

  3. What do the Comfortis reviews say?

    Comfortis reviews rated 5 out of 5 stars. Most reviewers say that Comfortis is the best flea treatment out there but can be impossible for their pets, especially cats, to take every month. Once treated, pet owners don't see fleas anymore on their dogs or cats.

  4. What Comfortis dosages are available?

    Dogs and cats are administered a dosage of 13.5 mg/lb (30 mg/kg) per tablet. See the chart above for various dosages and box colors per weight.

  5. Is Comfortis Flea Preventative for small dogs (i.e., puppies) and kittens?

    Comfortis can be used by puppies or kittens that are at least 14 weeks and older. It's approved for cats that weigh a minimum of 4.1 pounds and dogs that are 5.0 lbs.

  6. What are the most common Comfortis side effects?

    Vomiting and anything associated with vomiting. A pet that vomits within the hour of administration of Comfortis must be given another full dose of a chew. Other observed side effects can be itching, diarrhea, decreased appetite, depression, incoordination/trembling, hypersalivation, or seizures.

  7. How long does it take for Comfortis to work?

    Comfortis starts working and killing fleas after 30 minutes and works for 30 plus days. In a controlled laboratory study after four hours, Comfortis kills 100% of fleas on dogs and 98% of fleas on cats.

Concluding Thoughts

The most important thing that you should know about Comfortis is that this seems to be the best flea treatment out there for dogs AND cats. This revolutionary monthly, beef-flavored oral chewable starts working and killing fleas after 30 minutes after treatment and it is beloved by pet owners that don't have to wait to touch their pets, to allow for their pets to play or get wet, don't have to isolate them from other non-treated pets, or to worry about stains on their furniture or clothes.

DISCLAIMER: FDA law restricts Comfortis Flea Preventative only on order or prescription of a licensed veterinarian for the best pet health care advice. Ask your veterinarian or consult with one of our pet care specialists at 1-800-844-1427.

This informative article is not meant to substitute for the diagnosis, treatment, and professional advice from your veterinarian or other qualified professionals regarding a medical condition. Ask your veterinarian if it's a good idea to treat all of the animals in your household to control a home flea infestation.

  • Elanco Animal Health Brand
  • Flea & Tick Pharmacy
  • Comfortis Pharmacy Brands
  • Protection Wellness Philosophy
  • Flea Allergy Dermatitis Skin & Coat Health
  • Ivermectin Sensitivity Allergies
  • Prescription Pharmacy Type
  • Giant Breed Pet Size
  • Elanco Animal Health Manufacturer
  • X-Small Breed Pet Size
  • Small Breed Pet Size
  • Medium Breed Pet Size
  • Large Breed Pet Size
  • Oral Application
  • Cat Pet Type
  • Dog Pet Type

Is Comfortis for ticks also?

Yes, Comfortis is for ticks as well as fleas. Note that the primary use of Comfortis is for flea treatment. It is an excellent FDA-approved flea medicine that can help get rid of fleas from your dogs and cats. And while it can be used on your dog or cat for ticks, it is mostly marketed as a medication that kills fleas. Comfortis can only claim that it is an effective tick-killing or control drug once clinical tests have been conducted and approved. Till then, the medication will only brand itself as a flea-killing medicine.

What does Comfortis protect against?

Comfortis protects against fleas as well as ticks. Comfortis is a packet of chewable tablets that your vet will recommend if your dog or cat has fleas. The active ingredient Spinosad, which is a popular insecticide, is used in the making of Comfortis. This active ingredient is a natural substance that can lead to the paralysis of fleas on the dog or catโ€™s body. Comfortis will get rid of the fleas before they can lay eggs. Comfortis also protects against ticks. However, since the company has not yet received clinical approval for its tick protection, it cannot advertise Comfortis as a tick-killing agent. Talk to your vet to see if you can use Comfortis for ticks in your pet.

Does Comfortis really work?

Yes, Comfortis really works. Many pet medications take time to start working their magic. Some take about a couple of weeks, while others can take more than a month. In some cases, pet medications will not give you the expected results, even after you have waited for months. Comfortis, however, is not like that. These chewable tablets start working within 30 minutes. You can see the results right in front of you and do not have to wait for weeks or months to understand whether or not the medication is working. Clinical tests suggest that Comfortis is 99 percent effective, and works quicker than most pet medications.

How effective is Comfortis?

Comfortis is 99 percent effective. Comfortis is a flea (as well as tick) control medication for dogs and cats. It shows a hundred percent effectiveness in dogs and a 98 percent effectiveness in cats when it comes to killing fleas. These effectiveness scores have been obtained from clinical lab studies. The results start showing within 30 minutes of usage. Effectiveness can vary in the real world, but not to a great extent. It may differ by some margin depending on the type of infestation on your dog or cat.

Which is better, Comfortis or NexGard?

Comfortis is better than NexGard. Both Comfortis and NexGard are guaranteed to give a hundred perfect relief from fleas. Hence, you cannot separate these two here. However, NexGard takes around 24 hours to start working. That means it will take an entire day to relieve your pet of its fleas. Comfortis, on the other hand, shows results within just 30 minutes, and it has been proven in lab tests as well. So, Comfortis is the superior medication when compared to NexGard.

Can Apple cider vinegar kill ticks?

Apple cider vinegar does not kill ticks, but it does help to repel them. Bugs and pests hate apple cider vinegar. It is a natural way to keep these nasty little things at bay. The vinegar may not kill ticks or fleas, but its presence helps to drive them away. It also prevents further infestation, at least for some time.

How often do you give Comfortis?

Comfortis is given once a month, with a minimum dosage equal to 50 mg/kg, or 22.5 mg/lb. Comfortis shows its work within just 30 minutes of intake. It is very effective, which is why you can make do with just one dose per month. However, continue the dosage as prescribed by the vet. Missing the dose can hamper the treatment cycle.

How long does the Comfortis pill last?

Comfortis lasts a whole month. Comfortis starts working its magic within 30 minutes of administration. It also lasts a whole month, which means you just need to ensure monthly dosages.

Should Comfortis be given with food?

Yes, Comfortis should be given with food for maximum effectiveness. Given that it is flavored, your pet will have no trouble consuming the medication through food.

What happens if you give your dog too much Comfortis?

If you give your dog too much Comfortis, it will overdose on it. Comfortis overdose can lead to vomiting. Consult a vet immediately if the vomiting does not stop.

How do I protect my pet from fleas?

Fleas are a common problem for pets. Fortunately, there are several ways you can protect your pet from these pesky insects. Talk to your veterinarian about the most suitable flea prevention products for your pet. There are many different types of flea prevention products available, including topical treatments, oral medications, and flea collars. Regularly vacuum your carpets and upholstery to remove flea eggs and larvae, and wash your pet's bedding and toys in hot water. Keep your yard trimmed and remove any debris that could provide a breeding ground for fleas. Regularly inspect your pet's coat for signs of fleas, including small black or brown specks, and if you notice any signs of fleas, take action immediately. Fleas can easily jump from one animal to another, so it's important to keep your pet away from other animals that may have fleas. If you do find fleas on your pet, take immediate action to treat the infestation. This may involve using a flea shampoo, flea spray, or flea comb.

What should I give my dog for flea prevention?

There are several options available for flea prevention in dogs, including topical treatments, oral medications, flea collars, and flea shampoos/sprays. Topical flea preventatives are applied to the skin between the shoulder blades or at the base of the neck and include products such as Frontline, Advantage, and Revolution. These products typically need to be applied monthly and work by killing fleas on contact. Oral flea preventatives are taken by mouth and include products such as Comfortis, Trifexis, and NexGard. They work by circulating in the bloodstream and killing fleas when they bite the dog. Oral flea preventatives typically need to be administered monthly. Flea collars are infused with flea repellent and can provide several months of protection against fleas. Some common brands include Seresto, Hartz, and Adams. Flea shampoos and sprays can be used to treat existing flea infestations but do not provide long-term protection against fleas. Some common products include Adams Flea & Tick Shampoo and Vet's Best Flea & Tick Spray.

What is a natural flea preventative?

There are several natural flea-preventative options that you can try for your pet. While these may not be as effective as some of the conventional flea preventatives, they can still be useful as part of an overall flea prevention strategy. You can dilute 1 part apple cider vinegar with 1 part water and use it as a spray on your pet's coat. The strong scent can repel fleas and help prevent infestations. Certain essential oils, such as lavender, peppermint, and citronella, can be used as flea repellents. Mix a few drops of the essential oil with water and use it as a spray on your pet's coat or on their bedding. Diatomaceous earth is a natural powder made from the fossilized remains of tiny aquatic organisms. It can be sprinkled on your pet's coat or on their bedding and acts as a desiccant, dehydrating and killing fleas. Herbal flea collars are infused with natural flea repellents such as cedarwood, eucalyptus, or lavender. They can be an effective natural flea prevention option, but it's important to choose a reputable brand and follow the manufacturer's instructions carefully.

What smell do fleas hate?

Fleas are sensitive to certain smells, and there are several scents that they may find unpleasant or repellent. Citrus fruits such as oranges and lemons can be used to make a spray or solution to help repel fleas. Lavender is a natural flea repellent and can be effective at repelling fleas. Peppermint oil is another natural flea repellent, and it can be mixed with water and used as a spray on your pet's coat or on their bedding. Eucalyptus oil or fresh eucalyptus leaves can also be used to help repel fleas. However, remember that while these scents may help repel fleas, they may not be as effective as conventional flea prevention products.

What kills flea eggs?

Flea eggs are resistant to many insecticides, and they can be difficult to kill. However, there are several products that can help to kill flea eggs and prevent them from hatching into adult fleas. Insect growth regulators (IGRs) are chemicals that disrupt the growth and development of flea eggs, larvae, and pupae. They prevent the eggs from hatching and developing into adult fleas. IGRs are available in the form of sprays, shampoos, and spot-on treatments. Some insect growth regulators (IGRs) that are commonly used for flea prevention and control include Comfortis, Frontline Plus, Advantage II, Program, and Sentinel. These products contain IGRs and other active ingredients that help kill and prevent fleas at all life stages. Regular vacuuming of your home can help to remove flea eggs and prevent them from developing into adult fleas. Vacuuming should be done frequently, especially in areas where your pet spends a lot of time. Steam cleaning can be effective at killing flea eggs and larvae in carpets, upholstery, and other fabrics. The high temperature of the steam can kill the eggs and prevent them from hatching. Diatomaceous earth can also be sprinkled on carpets, upholstery, and other fabrics to kill flea eggs and larvae.


Comfortis side effects are associated most commonly with vomiting. Other possible reactions are depression, decreased appetite, diarrhea, itching, trembling, hypersalivation, and seizures. Comfortis may be used concurrently with heartworm prevention products, as they are directed.

Ask your veterinarian or consult with one of our pet care specialists at 1-800-844-1427.

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian. Always seek the advice of your veterinarian or other qualified professional with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website. Our medications are FDA approved and/or EPA regulated when and as required by law.

Administer correct dose monthly, as prescribed by your veterinarian, with food, year-round without interruption. If you miss a dose, immediately administer Comfortis and resume regular monthly dosing.

Store Comfortis at room temperature.

Comfortis is manufactured by Elanco Animal Health
Option UPC/SKU
Dogs - 5-10 lbs. or Cats - 4-6 lbs., 6 months supply 309864222062
Dogs - 10-20 lbs. or Cats - 6-12 lbs., 6 months supply 309864223069
Dogs - 20-40 lbs. or Cats - 12-24 lbs., 6 months supply 309864224066
Dogs - 40-60 lbs., 6 months supply 309864225063
Dogs - 60-120 lbs., 6 months supply 309864227067

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