Pyrethrin and Pyrethroid Poisoning in Dogs

What are pyrethrins and pyrethroids?

Pyrethrin insecticides are naturally derived from the chrysanthemum (“mum”) flower, and pyrethroids are the synthetic (artificial) versions of this chemical. Pyrethroids are commonly found in products used around the home for insect control, including:

• Home and outdoor yard and garden insecticides (these typically come in liquids, sprays, granules, and foggers)
• Over-the-counter medicated flea shampoos
• Topical flea and tick preventatives

How poisonous are these insecticides to dogs, cats, and other animals?

Whether or not a pyrethrin or pyrethroid product is toxic depends on the species, the concentration, and the other ingredients that make the product effective (synergists and carrier). The use of pyrethrins or pyrethroids is generally safe in dogs, but cats and fish are very sensitive to these products.

Life-threatening signs may be seen in cats with even a very small exposure to products containing pyrethroids. Fish may die from even the smallest exposure, so be sure to cover aquarium tanks with something non-porous, like plastic wrap, or remove the tank from any area you treat with a pyrethrin or pyrethroid product.

If you apply a topical flea and tick preventative treatment to your dog, do not allow them to jump into a body of water where fish may be living for at least 24 to 48 hours after application.

How do dogs become exposed to pyrethrin or pyrethroid insecticides?

Topical flea and tick spot-on medications often contain high concentrations of pyrethrin or pyrethroids and are commonly used on dogs without serious problems. Dogs may also be exposed to lower concentrations when these products are used inside or outside the home in the form of insect sprays, foggers, and granules. These products when used as instructed are generally safe in dogs, but poisoning can occur if they are used improperly or if a dog ingests them.   

What are the signs of pyrethrin or pyrethroid poisoning?

In dogs, signs of poisoning can develop in the first hour after ingestion, and may include any or all the following signs:

• Excessive drooling
• Gagging or hacking
• Vomiting
• Lack of appetite
• Agitation

Dogs can develop severe neurologic signs, including tremors and seizures, if they are more sensitive to pyrethrins and pyrethroids, are exposed to bifenthrin, or ingest a large or concentrated amount.

Pyrethroid-based topical flea and tick products, especially spot-on formulations, may cause paresthesia or a “pins and needles” sensation of the skin. This sensation typically occurs where the product was applied to the dog (e.g., along the back). Although this is not usually a significant concern, it can be uncomfortable and stressful for your pet. Signs can develop within 15 minutes to several hours after the product is applied to the dog’s skin.

Signs of a skin reaction in dogs may include:

• Agitation or restlessness
• Intense itchiness
• Rolling around on their back or trying to bite at their back
• Vocalization
• Crying or whimpering

What should I do if my dog is showing these signs?

If you suspect that your dog is having a reaction to a pyrethrin or pyrethroid, immediately call your veterinarian or Pet Poison Helpline, a 24/7 animal poison center, at 1-800-213-6680, to determine if there are at-home treatments you can perform or if immediate veterinary referral is needed.

Additionally, if your pet is having a reaction to a flea or tick product, call the product manufacturer. Many animal health companies offer 24/7 support in case of adverse events. The sooner you seek treatment, the better the prognosis and outcome for your pet.

How is pyrethrin or pyrethroid poisoning diagnosed?

Your veterinarian will make a presumptive diagnosis if there is a known or possible history of exposure to a product containing a pyrethrin or pyrethroid, coupled with the expected signs.

How is pyrethrin or pyrethroid poisoning treated?

There is no antidote for pyrethrin or pyrethroid poisoning. However, quick and effective treatment with decontamination, monitoring, and supportive care help minimize the extent and severity of signs.

If clinical signs have developed, then treatment will be based on the active ingredient your pet was exposed to, how your dog was exposed to the product, and the signs that your dog is showing. Your veterinarian may bathe your dog with liquid dish soap to remove any remaining product and prevent further exposure.

In cases involving more severe signs, your dog may require hospitalization for 48 to 72 hours. In some cases, signs can seem to resolve but then reoccur, so it is important for your veterinarian to monitor your pet and provide supportive care. Supportive care may include intravenous fluid therapy and medication for the animal’s specific clinical signs. Your veterinarian will also monitor your dog's temperature, blood glucose levels, and kidney function.

What is the prognosis if a dog has severe pyrethrin or pyrethroid poisoning?

If your veterinarian can provide prompt, early treatment, the prognosis is usually good. However, if the dog develops uncontrolled neurological signs, clotting problems, or kidney issues related to seizures or elevated body temperature, then the prognosis can be poor.

How can I protect my dog from this poisoning?

With any poisoning, rapid diagnosis and treatment is imperative.

• To prevent accidental exposure, read the directions for any product carefully before use.
• Be cautious about the number of different flea or tick products used on your dog, as many products are not designed to be used in combination with other products. 
• If you have a flea infestation, call your veterinarian to discuss proper and safe treatment for your pets and your environment.
• Use the appropriate flea and tick preventative for your dog's weight range. Do not use part of a larger-sized dose, or multiple smaller doses, as this may result in an overdose and increased chances of poisoning. When in doubt, bring your dog to the veterinarian for a weigh-in. 
• Store all pyrethrin or pyrethroid products safely and out of reach of your pets.
• Never use an insecticide on a pet that is not intended to be used on animals. Even if the concentration of insecticide is low, the carriers or other components may be harmful to animals.
• Keep your dog away from any areas, both indoors and outdoors, that have been treated with a pyrethrin or pyrethroid product until it has completely dried.

Pet Poison Helpline, an animal poison center based out of Minneapolis, MN, is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals, and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s per-incident fee includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com.