How Do Flea Collars Work?

  • Written By Dan Edwards on November 10, 2018
    Last Updated: December 10, 2020

An infestation of fleas in your pet is unpleasant for both pet and owner. When it comes to parasites, prevention can be better than a cure. There are a wide variety of products on the market for preventing and killing fleas. Popular choices include spot-on targeted medications such as sprays, or oral tablets.

Flea collars are one such potential deterrent against these troublesome parasites. These are a special type of collar to protect your dog or cat from fleas. I’m going to detail how flea collars work and how effective they really are. You will also learn how to use flea collars to their best advantage to keep your companion flea-free.

How Do Flea Collars Work?

To make one of these devices, an insecticide is combined with plastic resins and molded into a thin strip (the collar). This might sound like a straightforward process, but a lot of deliberation goes into creating a flea collar. The insecticide and even the type of plastic have to be carefully chosen with a few criteria in mind.

Firstly, and most importantly, the chemical cannot be one that is toxic to dogs or cats. As these collars are intended to be worn for months, the pesticide should not irritate skin. It must be non-toxic, even if ingested, in the event of your pet removing the collar and chewing on it.

The next essential specification is that the pesticide of choice has to be effective. Despite being non-toxic to animals, it still has to be potent enough to kill and stave off fleas. The chemical must remain stable in all the environments that your pet may be exposed to. For example, hot and cold weather, rain, etc. It should not have a distinct chemical smell that could bother your pet.

The plastic that will make up the collar itself has to be compatible with the insecticide. It should have the right composition to release the main ingredient gradually at a stable rate. If too little insecticide is released, your pet won’t be protected. Too much at once, and the collar will be useless in a very short time or be potentially dangerous to your pet.

Flea collars can deliver the insecticide in either liquid or solid form. Liquid insecticides release from the flea collar in the form of a vapor. However, liquid flea collars must be manufactured with extreme caution. Rapid release can lead to vapor droplets collecting on the collar’s surface. If these droplets are ingested by your pets, they could be toxic.

Solid insecticides can be released through friction. Molecules of the chosen insecticide accumulate on the surface of the collar. These molecules are then displaced naturally through the collar’s contact with your pet’s fur. Insecticide in the collar constantly rises to the surface, meaning there is a self-replenishing pesticide supply.

The collar’s plastic also has to be tough enough to withstand daily wear and tear. After all, your pet is going to be sporting the collar for a minimum of three months. Finally, the collar has to be convenient for use for you and your pet. It shouldn’t stain your pet’s fur or rub off on bedding or furniture.

There is no universal flea collar appropriate for every pet. The type and dose of insecticides in the collars depend on the species and size of your companion. Large breed dogs will require a much higher dose of insecticide than a small breed of dog or a cat.

Appearance-wise, most flea collars are functional rather than frivolous. The plastic of the collar might be treated with a lubricant and colorants to give it an aesthetically pleasing look.

How Effective are Flea Collars?

Flea prevention is not to be taken lightly. As they are bloodsuckers, fleas are itchy and uncomfortable for your companion to have. These parasites can transmit diseases to your pet, such as leishmania infantum. Your dog can contract this infection when bitten by certain types of fleas, and it can be contagious to human beings.

flea bites on dog belly
Flea bites on a dog’s underbelly

Before I delve into the efficacy of flea collars, let us briefly consider overall treatment. There are a few factors that contribute to your success in treating these parasites, regardless of the treatment method. Fleas are opportunistic parasites that multiply quickly and can affect any area of the animal’s body.

Therefore, keep in mind the following considerations. Firstly, any flea treatment should be capable of targeting all areas of your pet’s body. Secondly, the medication should kill the fleas as rapidly as possible. Finally, the treatment should be effective long-term. Preferably, it should have the ability to repel as well as kill.

One study compared the effectiveness of flea collars on dogs over 226 days. The active ingredients in the collars were imidacloprid-flumethrin (IVP), and deltamethrin (CP1).

These are both commonly used insecticides in medicated, slow-release collars. The purpose of a flea collar is to protect the animal consistently – meaning 24 hours a day.

The results revealed that these collars were 90 to 100 percent effective, even after 70 days. A similar study on cats revealed that IVP flea collars were approximately 98 percent effective at preventing and treating infestations for eight months.

Another trial monitored the effect of flea collars on both cats and dogs. A total of 313 cats and 400 dogs were treated with either IVP collars or CP formulated collars. The animals were examined regularly over eight months to check for fleas.

By the end of the eight-month trial, both cats and dogs benefited from a significant flea count reduction. The flea collars were found to be effective in treating the occasional natural infestation and preventing fleas overall. The collars were confirmed as safe for pets from the ages of seven weeks old (puppies) and 10 weeks old (kittens).

Animals that spend a lot of time outdoors are more exposed to the possibility of a flea infestation. Outdoor cats, in particular, have a good chance of contracting fleas if they don’t have protection.  The effectiveness of IVP collars in outdoor cats was monitored for 12 months. By the end of the year, all cats benefited from a 79 to 100 percent reduction in fleas.

fleas on cat's stomach
Fleas on a cat’s stomach

Even in areas where fleas are endemic, flea collars have shown success as a preventative and a cure. Flea collars were given to roughly 200 dogs living in a hyper-endemic area, meaning the risk of a flea infestation is extremely high. All the dogs were monitored periodically over 200 days.

Dogs wearing IVP collars were 100 percent free of fleas during all check-ups. The dogs that were wearing CP collars had infestations of between 23 to 33 percent. However, this was still a big decrease compared to no protection at all.

These medicated collars also offer protection for dogs living in high-risk communities. These include animal shelters and boarding kennels. One study used flea collars to treat dogs in animal shelters suffering from heavy flea infestations. After two days, only 11 percent of the treated dogs still had fleas.

Flea medications have to work against both adult and young fleas. Flea collars are potent against fleas at all stages of their development. On dogs, flea collars were found to successfully repel over 90 percent of both adult fleas and flea larvae for eight months.

Flea collars also work rapidly to combat any existing infestations. After only two days, the collars were between 99.8 to 100 percent effective at killing off fleas on the dogs.

How to Use Flea Collars Effectively

As an owner, you play a role in how successful the treatment outcome is. It is important to follow treatment guidelines explicitly, even if it may be difficult for you and your pet. Other treatments such as flea shampoo can also be used effectively in conjunction with a flea collar.

Flea collars have the advantage of easy usage. The collar itself does all the work for you – all you have to do is put it on.

Flea collars are usually a standard size when it comes to width and thickness. The collars are sold a little longer than necessary. This is to enable you to fit it to your pet’s neck exactly, and trim off any unnecessary length.

When it comes to choosing a flea collar, safety comes first. There are different precautions to think of, depending on whether you have a cat or a dog. Outdoor cats can get their collars caught in tree branches or other items. There have been incidents of cats being strangled by flea collars.

Make sure the collar you purchase is cat-safe and will either break or allow your cat to escape if stuck. If you have both cats and dogs, check that the collar is non-toxic for both animals. This is because the active ingredients in collars differ, depending on the size and species of your pet. A collar for a large breed dog can be toxic to smaller dogs or cats if they lick it.


Do flea collars work? Yes, they do, if you choose the right one. They are an effective, easy-to-use prevention against fleas. They are also capable of fighting flea infestations without any intervention on your behalf. Always check with your vet before using a flea collar on your pet. If your pet is sensitive or has an existing skin condition, a flea collar might not be the best option.