Do Flea Collars Work?

Published Apr. 30, 2024
A dog with a flea collar.

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In This Article

What Is a Flea Collar?

Fleas are an extremely common and problematic external parasite (ectoparasite) affecting dogs, cats, and other animals with fur. Fortunately, today there are many safe and effective products on the market to treat and prevent flea infestations.

Flea collars have been available for a long time. With the advent of topical drops and oral prevention, flea collars have lost some popularity. However, they may still be the best choice for some pets and pet parents.

What Is a Flea Collar?

Flea collars consist of a plastic collar infused with anti-parasitic medications, which with prolonged contact are slowly released onto your pet’s skin. Depending on the product, these medications work to kill fleas that land on your pet and, in some cases, make your pet less desirable to land on.

While some collars kill only fleas, many now also protect against other ectoparasites like ticks, lice, and even some mites that cause certain forms of mange.

Some flea collars are permeated with oils, such as peppermint oil, or claim to use ultrasonic technology to repel fleas; however, only medicated collars have been proven to protect your pet.

While some collars kill only fleas, many now also protect against other ectoparasites like ticks, lice, and even some mites that cause certain forms of mange.

A few brands of medicated flea collars are available, but the Seresto® collar by Elanco™ is the only one with appropriate safety and efficacy studies and is most recommended by veterinarians to pet parents looking for a flea collar.

Flea collars are available for both dogs and cats. Some flea and tick preventatives that are safe for dogs are extremely toxic for cats, so make sure the collar you choose is labeled for your pet.

Depending on the product, some collars are safe to be used in puppies or kittens, usually over the age of 8 weeks.

How Do Flea Collars Work?

Modern flea collars work by holding a large concentration of anti-parasitic medication against your pet’s hair and skin.

This medication is slowly absorbed into the oil glands of the skin, which then distribute it around the body, where it affects any fleas it comes in contact with.

For example, imidacloprid and flumethrin—the active ingredients in the Seresto® collar—work against the nervous system of fleas and ticks, making it difficult for these parasites to attach to your pet’s skin and killing them if they do manage to bite.

Collars like Seresto® have been shown to be just as effective as topical drops and are even better at repelling fleas than some of the oral preventative options.

It takes about 24 hours for a new collar to start working against existing fleas, and then any new fleas that attach are killed within two hours. Other brands will have different onsets and mechanisms of action.

Collars like Seresto® have been shown to be just as effective as topical drops and are even better at repelling fleas than some of the oral preventative options.

Are Flea Collars Safe?

Flea collars provide the longest continuous protection available. Oral products and other topical products need to be reapplied every one to three months, while most flea collars advertise more than five months of protection. This also makes them very cost-effective.

Though you should still wash your hands after handling flea collars directly, many pet parents appreciate avoiding the mess of topical drops and the ease of application of the collar.

Unfortunately, flea collar safety is widely variable.

Bayer and Elanco™ have invested in many studies, making sure that Seresto® is a safe and effective product. Other brands have less information available about safety and risks.

No matter the brand, using a flea collar inappropriately (for the wrong size pet or species) can certainly be dangerous.

The majority of the risk of flea collars is with inappropriate usage. Risks to pets with a recommended product used as intended is minimal. Applying a collar too tightly or using a product that is not designed to break under pressure can lead to strangulation and skin damage.

Leaving the collar too loose or taking the collar on and off repeatedly will lead to decreased efficacy. With growing animals, it is extremely important to remember to resize the collar as they age and make sure they don’t grow out of the collar’s effective weight range.

Because collars work topically, pets who swim regularly or are bathed more than once monthly may need their collar replaced more frequently.

Some studies have linked long-term use of tetrachlorvinphos-containing flea collar products with an increase in oral cancer, such as squamous cell carcinoma, in cats. The specific brands of flea collars implicated have not been listed. There are no known risks to dogs with long-term flea collar use.

Should You Buy a Flea Collar?

When recommending a parasite prevention program for your pet, your veterinarian will focus on safety, efficacy, and how a product fits your lifestyle and budget. There are absolutely situations where a flea collar is the best recommended product.

There are no flea collars available on the market for pets less than 7 weeks of age, and be cautious with the use of collars in growing pets.

Current flea collars are marketed for dogs and cats, and use on other species (including humans) is not recommended.

Because most flea collars work topically, there are no commonly known drug interactions with most flea collars.

Be sure to discuss your pet’s medication and health history with your vet before choosing a product.

Alternatives to Flea Collars

If a flea collar does not sound right for your pet, there are many other proven products available for flea prevention. Advantix® II for dogs, Advantage™ for cats, and Frontline® Plus are great topical drop products available at most retailers.

You can also discuss prescription topicals like Revolution®, Revolution® Plus, NexGard® Combo, Advantage Multi™, and Bravecto® (topical) with your veterinarian.

Oral products for dogs like Bravecto®, NexGard®, and Simparica™ treat both fleas and ticks.

Sentinel®, Trifexis™, and Simparica Trio™ combine flea prevention with your dog’s monthly heartworm prevention. Credelio™ is available for cats who tolerate oral medications.

Jamie Lovejoy, DVM


Jamie Lovejoy, DVM


Dr. Jamie Lovejoy graduated from Tufts Cummings School of Veterinary Medicine in 2012 after an undergraduate degree in Marine Biology. ...

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