Simparica vs. Comfortis: 2024 Comparison and Key Differences

When your pet has fleas you’ll notice frequent scratching, whining, and general discomfort. Your pet’s fleas problem won’t go away on its own and your vet can provide you with a few options. So, how do you choose?

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Flea medications come with several features and the dreaded side effects. Veterinarians commonly recommend medications like Simparica and Comfortis, but it is up to you to decide which medicines are best for your pet, your budget, and your schedule. Understanding the active ingredients and how they work to make you a knowledgeable pet owner.

Some flea medications are safe for both dogs and cats, while others are approved for one type of animal. Flea medications often include ingredients that kill other parasites like heartworms or ticks. But, with added ingredients come extra side effects. Since the side effects of chewable pills include vomiting and diarrhea, you must decide what is important to you.

Before you make a choice, you should also take a look at the price of the medication. Since most pets do not have health insurance, any costs come right out of your wallet. You need to give some flea medications daily, while others are good for a month or longer. The prices of treating fleas with prescription medication can add up quickly.

What to look for in a good flea treatment

The best flea medications are easy to give to pets. They should be affordable and have limited side effects. They should also include ingredients that kill fleas quickly so that fur babies can find quick relief from the itching and scratching.

For many pet owners, chewable medication is the best option. Manufacturers are making chewables that taste good, so dogs and cats do not fight you while taking their medication. Other options, like creams and collars, can be challenging as pets will chew on them and fight the applications.

Before you choose, look at how the treatment deals with fleas. Some medications attack fleas so they cannot reproduce; this stops the life cycle in its tracks. Other medications poison the fleas, so they die within an hour of taking the drug.

The best medications kill fleas quickly and prevent them from reproducing. If your pet has sensitive skin, you might want to avoid a topical product. But, if your pet will not take a tablet, then a topical treatment is a practical choice – so find one with soothing ingredients like aloe or oatmeal.

Only buy medication that is designed for the size and age of your pet. Some medications are not made for pets under a certain age or weight. Most are made for pets that are at least four weeks old, so ask your veterinarian if you have a young puppy or kitten.

Simparica and Comfortis Similarities

Simparica and Comfortis are commonly prescribed for dogs. They are both FDA-approved, chewable tablets that must be prescribed by a veterinarian. They are both given in monthly doses.

Both medications have similar side effects. The most common in both are diarrhea and vomiting. Side effects are rare, but they can also include problems like trembling, ataxia, and seizures.

Pets can get fleas even if they do not go outside. It is also possible to get fleas during cold months, as fleas can live in warm homes. So, dogs and cats might need to take flea medication at any time of the year. Both of these medications can be taken in any season.

Simparica and Comfortis are in tablet form, and they both have a meat flavor that pets like. Simparica has a liver flavor, while Comfortis has a beef flavor. To reduce the likelihood of side effects, veterinarians recommend taking the tablet with a full meal. These medications are the least messy, even after you consider the side effects.

If your dog or cat needs a topical treatment, you might have to isolate your pet from your family until the flea medication has settled. But, with a tablet like Simparica and Comfortis, you do not need to isolate your pet. You should keep the medication away from children, who should not take it. But, once pets ingest it, they can get right back to playing and enjoying life.

Simparica and Comfortis Differences

Even though the two medications are meat-flavored tablets that are taken monthly, there are several differences between these flea treatments, including their active ingredients.

Simparica uses sarolaner, a neurotoxin that creates spasms in the parasitic insect. The fleas can no longer breed. While side effects are low, some dogs that take Simparica do develop digestive problems.

Comfortis includes spinosad, another neurotoxin that affects the parasitic insect’s nervous system, preventing it from eating. They cannot lay eggs, so infestations end when the young fleas reach adulthood and die. This usually takes about three months.

Simparica is only available for dogs, and they should be at least six months old. Pets should be at least 14 weeks old before taking Comfortis. There are other options available for younger dogs. Comfortis is available for dogs and cats. The lines are separate, with chewables designed for different weights and ages.

Both medications effectively treat flea infestations, but Simparica will also kill ticks. Simparica begins to kill fleas within three hours of treatment. And, it kills ticks within eight hours. Comfortis begins working within 30 minutes of ingesting the tablet. After four hours, Comfortis kills 100% of fleas on dogs and nearly 100% of fleas on cats, too.

Simparica and Comfortis Pricing Comparison

Comfortis is available in five packages for dogs and cats of different sizes. All five packages have six treatments; each treatment lasts one month. Three of the boxes are designed for dogs and cats, while two of the options are just for dogs.

Simparica is available in six different sizes for dogs. Each box includes six treatments. The treatments are less expensive than Comfortis.

Our Review of Simparica and Comfortis

Both are effective flea treatments. Comfortis is an excellent choice for cats and young puppies, but Simparica is slightly more effective. Dogs like the liver-flavored medicine better than they like the beef flavor. If you are looking for flea treatment for dogs over six months of age, Simparica is the right choice because it kills ticks, too.

If you have a cat, then you only can use Comfortis. Simparica is not designed for a cat’s anatomy, so you should not give it to them. Comfortis works well, even on small cats that weigh four pounds or more. If you have a smaller cat, ask your veterinarian for a different option.

Picky dogs prefer Simparica, so they are less likely to put up a fuss when you give them the monthly dose. The neurotoxin in Simparica has proven to be more effective on fleas than Comfortis. The active ingredient is also less likely to cause side effects, and most are digestive issues that don’t last long.

Another benefit of Simparica is that it is less expensive than Comfortis. If you are paying for separate tick and flea treatments for your fur baby, it might be time to ask your veterinarian if Simparica is a better choice. Your wallet will thank you.

Flea Treatment FAQs

Does my pet just need a flea treatment that kills adult fleas?

The short answer is no. Pets benefit from treatments that destroy fleas at all of their life stages. Adult fleas can spread tapeworms, so they need medications that kill them. But, it is also important to have treatments that kill the larvae, pupae, and eggs because there are more of them, and eventually become adults.

If I have several pets, do they all need flea treatments?

Yes. Fleas can move from one pet to the other. If one is scratching, then you can expect the others will be scratching soon. Cats and dogs can get fleas, so they both need appropriate treatments. Keep in mind that some pets will not scratch when they get fleas, simply because they may not have a sensitivity or allergy to them. But, this doesn’t mean they don’t have fleas.

If fleas are the same, can I use the same treatments on all of my pets?

No. Dogs and cats have different physiology, so they need different medications. Some brands make treatments that dogs and cats can take, but not all are approved for both animals
Cats tend to be more sensitive to treatments than dogs, so it is best not to mix medications. If you give your fur baby the wrong medication, you could accidentally poison it.

When will fleas die after I give my pet flea medication?

Some flea treatments will kill adult fleas within a few hours. Some take longer, depending on the type and strength of the active ingredient. If the medication targets younger versions of the parasite, then you might have to wait a few days before all of them are dead.

What are the most common side effects of flea treatments?

Oral flea treatments, like Simparica and Comfortis, have digestive side effects. Some pets will vomit or have bouts of diarrhea shortly after their owners give them a tablet. Pets sometimes lose their appetites. Usually, the side effects are short-lived. If side effects last longer than a few hours, you should talk to your veterinarian.

Other side effects can include other physical issues like lethargy, convulsions, or more scratching. Some pets suffer from ataxia, which is the inability to control their body movements; you might notice them struggling to walk. Most side effects do not require medication to treat; they stop after a few hours.


Pet medications are not all the same. Some target one issue, while some target several. When it comes to flea treatments, there are several to choose from. Comfortis is a flea treatment that is safe for dogs and cats, as long as they are 14 weeks old and over four pounds for cats and five pounds for dogs.

On the other hand, Simparica is available only for dogs, but they have to be at least six months old. This medication costs less than Comfortis, and it treats ticks, as well as fleas. Simparica kills both parasites in one convenient and delicious tablet. It is difficult to ignore the low cost and double duty.

Veterinarians frequently prescribe Comfortis and Simparica, so the choice is yours to make. For some pet owners, the flavor of the medication makes the choice easier. If your pet won’t eat the beef-flavored Comfortis but devours the liver-flavored Simparica, then your decision has become even more comfortable.

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