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By Jennifer Kvamme, DVM

If you and your pet spend a lot of time roaming outside during the spring and summer months, you have no doubt removed your fair share of ticks. Ticks are not only unsightly and gross, they can also carry diseases, transmitting them to your pet as they feed. There are many options available to repel ticks and keep your pet more comfortable during peak tick season.


Commonly used tick repellant products contain a widely used group of insecticides called pyrethrins. Pyrethrins take aim at the nervous system of insects by causing repetitious rapid nerve impulses, resulting in death. These chemicals have been used for more than 100 years to successfully repel insects.

Pyrethrins are naturally occurring chemicals, extracted from chrysanthemum flowers, and are not limited to tick control. They also can be used to control fleas, lice, some mites, and mosquitoes. Because they have a low toxicity, pyrethrins are used in products that can be applied directly to the pet’s skin. You can find Pyrethrins as active ingredients in shampoos, dips, powders, and spray formulations.

A synthetic group of chemicals similar to pyrethrins are the pyrethroids. These manufactured compounds have a longer-lasting effect and work in the same way that pyrethrins do, resulting in the death of insects as well as repelling insects. Pyrethroids are typically used with an oil carrier to be applied as a spot-on product for dogs. Cats are often sensitive to many pyrethroids, so care must be taken when choosing a proper tick preventive for your cat or kitten.

Citrus Extracts

Citrus pulp extracts (such as d-limonene and linalool) also cause a reaction in the insect’s nervous system, repelling them. You will find citrus extracts in shampoos, dips, and sprays. As they are created from a natural source, citrus-derived products may be less toxic, but they may also be less effective. As with Pyrethroids, be careful with citrus products, as cats are especially sensitive to citrus extracts.

Fipronil and Selamectin

A couple of the more recently developed synthetic chemicals that prevent fleas and ticks are fipronil and selamectin. These compounds cause a blockage of chemical transmission in the insect’s nervous system, leading to paralysis and death. They are usually mixed with an oil to be applied as a spot-on, allowing the product to stay in contact with the animal and release itself slowly over time. Selamectin has the added ability to absorb into the bloodstream, where it kills internal parasites as well, including the parasite that causes heartworm disease.

Carbamates and Organophosphates

Two compounds that work by inhibiting the normal function of a necessary enzyme in the insect’s nervous system are carbamates and organophosphates. These common chemicals are often used in conjunction with pyrethrins to delay their breakdown. Carbamates and organophosphates are found typically as active ingredients in tick sprays, dips, and collars.


One highly effective ingredient used in dog tick collars is amitraz. It is also found as an ingredient in dips used to treat mange. This chemical has no effect on fleas, but kills ticks by absorbing into the animal’s skin and will prevent ticks from attaching in most cases. Amitraz works by inhibiting signals in the tick’s nervous system. (Warning: Products containing amitraz should not ever be used on cats.)

While tick preventives may work the majority of the time, nothing is going to be 100 percent effective. It will still be necessary to thoroughly check your pet over from nose to tail after spending time in the great outdoors.

Image: Jerry Kirkhart / via Flickr

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