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What is Pyrethrin and Pyrethroid Toxicity In Dogs?

Written by: Adri Sandoval
Adri Sandoval is the Special Projects Manager for iHeartDogs and iHeartCats. Her work has deepened her love for animals, fostering a strong passion for rescue and animal advocacy.Read more
| Published on October 11, 2017

It’s important to use your dog’s flea and tick medication according to your vet’s directions, but do you know why?

Flea and tick control products contain insecticides that can be toxic if not used according to the label. They are meant for external use only, and can be dangerous if they’re swallowed or applied in larger doses than they’re meant to be. Remember, it’s a poison meant to kill the tiny bugs that want to make their homes on your dog, you only want to apply enough to be effective, but not harm your pet.

Fleas and ticks do more than just irritate your dog, they also transmit diseases including ringworm and Lyme disease. These are dangerous diseases, and prevention should be an important part of your dog’s care, but you should also be aware that being careless or using his medication in a way not advised by your vet can cause toxicity.

Symptoms of Toxicity in Dogs

The flea and tick control products available today can cause varying degrees of toxicity. Although the instructions usually state that it should be applied to the back of your dog’s neck where he can’t lick, it usually occurs due to ingestion rather than application, but either can be the reason for it. Different medications contain different toxic ingredients, and will cause different symptoms. If your dog is showing any of the following signs, your flea and tick medication may be the culprit.

Pyrethrins and Pyrethroids – The chemical pyrethrum, which is used to make these compounds, comes from the chrysanthemum plant

– Vomiting
– Tremors
– Difficulty breathing
– Profuse drooling
– Weakness
– Tearing of the eyes
– Diarrhea

More severe cases of poisoning might show these symptoms as well:

– Depression
– Fever
– Low body temperature
– Disorientation
– Respiratory failure can be followed by death

Indoxacarb (Oxadiazines) – Used alone in products for flea control, and in combination with permethrin in tick control. It’s in the same chemical class as crop pesticides.

– Excessive drooling
– Weakness
– Depression
– Abnormal walk and movement, inability to stand
– Head tilt

Organophosphates – These are made from phosphoric, or phosphoric acid. They amount of residue they leave and toxicity varies from one to the other. You’ll find organophosphates in many flea collars.

– Profuse drooling
– Small pupils (miosis)
– Frequent urination
– Muscle contractions (fasciculation)
– Lack of coordination
– Weakness
– Difficulty breathing
– Nervousness
– Diarrhea
– Vomiting
– Collapse can precede death

Remember – your dog’s medication is meant for dogs only. DO NOT attempt to use your dog’s medicine on your cat, the reaction and consequences will be much more severe.


Avoiding Pyrethrin and Pyrethroid Toxicity in Dogs

Toxicity is avoidable and relies heavily on using your dog’s medication wisely. Choose your flea and tick medication responsibly, and listen to your vet’s recommendations.

– Most medications say on the box that they are not for use in puppies. Be careful not to give your puppy a medication he isn’t old enough to use.
– Remember, more is not better. Do not give more than the recommended dosage and definitely DO NOT mix products.
– The directions included with the medication are for the safety of your dog. Be sure to read them.
– Many products are sold in dosages according to the size of the dog they’re meant for. Using too high a dosage for the size of the dog can cause a toxic reaction.
– Some pet owners may use a small amount of a tube meant for large dogs on their small dog to save money, not realizing that the dosage and strength can be wrong for a small canine.
– Ingestion of flea and tick medicine, whether by eating oral tablets or licking off a topical application, can be dangerous.
– Using an insecticide meant for humans (such as DEET for ticks and mosquitoes) that is not labeled for dogs.
– Do not use an out of date product, as regulations may have changed since it was manufactured.

Diagnosis of Pyrethrin and Pyrethroid Toxicity in Dogs

Onset of symptoms can come in only a few hours, or they may take a few days to show up. When you give your dog his flea and tick medication, it’s recommended that you record the date, amount, and time of use. It’s good information to have should your dog need to see a vet.


Your veterinarian should be able to form a diagnosis based on a blood test, urine samples, and symptoms, but may ask for the packaging of the product used, since detection through urine and blood isn’t guaranteed. If you can’t bring the packaging, knowing the name of the product and how much used can still be helpful. Even if your dog has been using the same medication for some time, he can still have a reaction.

Treatment of Pyrethrin and Pyrethroid Toxicity in Dogs

How your vet treats for toxicity will depend on a few things, including:

– The degree of toxicity
– Which product was used
– When the medicine was applied or given orally
– The age and overall health of your dog

After taking those things into consideration, and determining whether your dog is suffering from adverse nervous, muscular, neurological or respiratory effects, your vet will be able to treat your dog for poisoning. Some of the methods for detoxifying your dog are:

– A bath to remove the product if the toxicity is affecting the skin
– Some types of poisoning may be treated by inducing vomiting, though others will be best treated if vomiting is avoided
– Medication to clear your dog’s bowels may be given
– Your vet may give seizure drugs or muscle relaxants
– Active charcoal is often used to bind and eliminate stomach contents
– Intravenous medication could be necessary
– Oxygen, if your dog is having trouble breathing

Flea and tick medication is a must for a happy dog, but using it responsibly is entirely in your hands. Although off-the-shelf medications may seem convenient, the safest route is to buy from your veterinary clinic, so you can be sure you’re using unexpired, regulated medicines. Your vet can also advise you on safe dosages based on your dog’s specific needs. Again, your dog’s medications are only safe for your dog, and no other members of your family. More is not better, and can be dangerous if it exceeds the maximum dosage.

Always wash your hands after applying your dog’s medication, store them out of reach of pets and children, and you shouldn’t have any problems.


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