Is Comfortis for Dogs Safe To Use

Is Comfortis for Dogs Safe To Use

Author WDF Staff


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Proper flea protection is vital not only for your pet’s health but for your home as well. These pesky little parasites can take over your whole home if your dog is not well protected, and sometimes, topical protection simply doesn’t work. We can tell you that from personal experience.

One of our team members is called Astor, and he is a Swiss White Shepherd. His coat is so thick that traditional topical parasite protection, like Frontline or flea collars, simply doesn’t work. The only option he can take for protection against fleas is a chewable tablet like Comfortis. If you are thinking about including Comfortis in your dog’s life, here’s what you should know about it.

What is Comfortis?

Comfortis is an oral prescription medication that uses spinosad as its active ingredient. Its main goal is to get rid of fleas that infected your dog’s body. Comfortis comes as a chewable tablet most dogs find palatable. That makes it pretty easy to use. It also comes in different sizes and ready-to-use dosages. The only thing you have to do is make sure you got the right package.

IMPORTANT NOTICE: Comfortis is a prescribe-only drug, so you will have to get a prescription from a licensed vet. It is not safe for dogs under 14 weeks of age and less than 5 pounds of weight.

Is Comfortis effective?

One of the two most important questions regarding oral flea protection for dogs like Comfortis is, “Is it effective?” Giving your dog a medication that will not effectively protect against fleas doesn’t really make sense. Naturally, this is one of the first questions dog owners ask their vet.

dog on sofa

The good news is - Comfortis is very effective. In a Comfortis study, their oral flea medication started killing fleas in 30 minutes. Within 4 hours, 100% of fleas were dead. Even if you are not a vet, it is easy to conclude these numbers are pretty impressive. You can be sure your dog will be flea-free in a matter of hours if you decide to go with Comfortis.

Is Comfortis safe for my dog?

The second question dog owners ask their vet regarding this medication is, “Is Comfortis safe for my dog?” This is an entirely valid question since you are giving your dog a drug that contains insecticides. Plus, getting rid of fleas is not worth it if you end up with a dog that constantly has seizures. In that case, there would be better and safer solutions.

Luckily, Comfortis is considered a safe flea medication. All oral flea drugs can cause side effects and adverse reactions. Still, the vast majority of dogs on this medication showed little to no issues.

Comfortis side effects

Most oral flea medications, or for that matter, all medications, can cause side effects; Comfortis is no different. Some of the most common Comfortis side effects are;

  • Vomiting
  • Incoordination
  • Diarrhea
  • Itching
  • Trembling
  • Excessive salivation
  • Seizures
  • Loss of appetite


Just because these side effects are possible doesn’t mean your dog will necessarily develop them. It just means that some dogs had them, and the company stated that in their documentation.

How is Comfortis given to dogs?

As we already mentioned, Comfortis comes as chewable tablets, making it really easy to use. Another great thing about it is that it leaves no pesticide-like residue on your dog’s coat, and you can bathe your dog immediately after giving them the medication. Bathing or swimming will not reduce the effectiveness of the drug.

Comfortis will keep fleas off your pet for an entire month. In fact, the protection period lasts for about 35 days. Vets usually recommend you give one tablet at the beginning of each month for complete protection.

Where can I get Comfortis?

Since this medication can only be prescribed by a licensed vet, the best way to get it is by taking your dog for a checkup. Your vet will write you a prescription, and you can easily pick Comfortis up at your local pet pharmacy. Another easy way to get it is on Chewy. However, you will need to present a valid prescription. Here are the links for a quick order;

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