Major Uses

Pyrethrins are a class of drugs made from the extracts of chrysanthemum flowers. They are a very common ingredient in flea and tick control products due to their ability to affect an insect's nervous system and cause death. Pyrethrins are typically combined with other drugs to increase their action and reduce side effects.

Pyrethrins are primarily used to control fleas, ticks, mosquitoes, and lice on dogs. They are highly toxic to felines and should be used with caution to control fleas and ticks on cats.

Common Precautions

Skin irritation or sensitivity at the site of application is fairly common. If bothersome, the animal's skin and coat can be bathed with a mild soap and then rinsed well with plenty of water.

This product is primarily for use on dogs. Although formulations are available for use on cats, it is not recommended that pyrethrins be used on cats without close veterinarian supervision due to a high potential for overdose. Pyrethrins are toxic to cats in small amounts.

Pyrethrins should not be applied to the mouth, eyes, or genitalia of animals, and they should not be used in animals less than 12 weeks of age.

Pyrethrins may interact with other drugs or supplements. It is important to disclose all current and recent medications and supplements to a veterinarian before beginning treatment with pyrethrins.

Pyrethrins should not be used in animals with a known allergy or hypersensitivity to the drug. Even a small amount of pyrethrins can cause serious or fatal effects in cats. Signs of overdose may include vomiting, profuse drooling, hyperexcitability, weakness, tremors, agitation, seizures, breathing problems, and others. Without immediate medical attention, pyrethrin toxicity can be fatal. In dogs, overdose generally causes scratching, tingling, drooling, and other symptoms. Any known or suspected overdose should be reported to a veterinarian right away.


Pyrethrins should be stored at room temperature, away from children and animals, and far from heat sources or open flames. This product is toxic to fish and should never be disposed of in bodies of water or down drains.


Pyrethrins is available in a variety of formulations for topical application to the skin of animals.

The dose of pyrethrins depends on the specific formulation being used. Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose of pyrethrins is missed, it should be applied as soon as possible. If it is almost time for the next dose, the missed dose should be skipped and a normal schedule resumed. Two doses of this drug should never be applied at once.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.