Antifreeze Toxicity


When the cold weather returns antifreeze becomes a more common danger to our pets.   Pet owners need to take precautions against the life threatening toxic effects this chemical can have on our pets.  Prevention is key as death can occur in as little as 12 hours after ingestion.  Early recognition of exposure and prompt veterinary attention is essential!


Antifreeze toxicity occurs when a pet ingests a chemical containing ethylene glycol.  Antifreeze often has a sweet taste, unfortunately attracting pets and encouraging them to taste and consume it.  Ethylene    glycol is not only found in antifreeze, but can also be found in radiator coolant, windshield deicing agents, brake fluid, motor oil, developing solutions for hobby photographers, wood stains, solvents, and paints.  The concentration of ethylene glycol in these compounds varies.

Only a small amount of ethylene glycol needs to be ingested to have toxic effects.  For cats, just a few licks can be fatal.  A teaspoon can be enough to kill a small dog.  The reason ingestion of this chemical can be fatal is the secondary effects the chemical has on the body.   Once ingested, the liver breaks down ethylene glycol into other toxic compounds that damage other organs.  The primary organs affected include the brain and the kidneys, with kidney failure being the ultimate cause of death.  The lungs and GI tract can also be affected.

The toxic effect of these chemicals can be broken down into the following 3 stages:

  • Stage 1:  Occurs 30 minutes to 12 hours after ingestion.  Signs usually indicate toxic effects on the brain as well as signs of intestinal irritation.  Symptoms include the following: vomiting, depression, walking with a wobbly gait, falling over, tremors, seizures, coma, and sometimes death.
  • Stage 2:  Occurs within 12-24 hours after ingestion.   Signs usually include increased breathing rate or effort and “open mouth breathing”.  A fast heart rate may also be detected in this stage.
  • Stage 3: Usually occurs within 24-72 hours after ingestion, but can occur as early as 12 hours depending on the amount of toxin ingestion.  Signs in this stage usually reflect damage to the kidneys and include vomiting, diarrhea, loss of appetite, oral ulcers, and decreased urination.


Because a pet’s likelihood for recovery worsens with each stage, the earlier a pet is treated for antifreeze ingestion, the better the prognosis.  Pets that are evaluated  and treated appropriately by a veterinarian within minutes to even 1-2 hours after ingestion have a good chance for a full recovery.  Pets that are not diagnosed until kidney damage has occurred have a much more guarded prognosis, need much more intensive care and treatment, and are at greater risk for developing permanent kidney damage or death.

What do you do if you think your pet ingested antifreeze?

If you suspect your pet ingested antifreeze, please take your pet immediately to your veterinarian for evaluation and treatment.  Antifreeze toxicity is diagnosed by a history of exposure, blood work and urine tests.  Ethylene glycol tests are available, but false negatives and false positives are possible.  If possible, please bring the antifreeze product with you so the veterinarian can determine if the antifreeze contains ethylene glycol.

How is ethylene glycol toxicity treated?

Treatment depends on the stage at which the toxicity is diagnosed.  Initially your veterinarian will need to perform some tests to identify how advanced the problem is, such as blood work and urine tests.  If ingestion or exposure was recent, your veterinarian may recommend making your pet vomit to remove any of the toxin from the stomach.   Your veterinarian may also give activated charcoal, an oral medication that binds to any toxin remaining in the intestines.

Based upon test results and the stage of presentation, your pet may be hospitalized to receive IV fluids and a medication (4-Methylpyrazole or 4-MP) to help prevent the liver from converting ethylene glycol to the toxic agents that cause kidney damage.   This medication needs to be given by injection and the complete course of treatment can take 2- 3 days.

If your pet has developed evidence of kidney damage by the time of presentation to your veterinarian, the recommended treatment plan may also include additional medication and hospitalization to help treat kidney damage.  In these cases, continuous nursing care and monitoring is recommended and gives your pet the best chance for positive outcome.  Your veterinarian may refer your pet to a 24-hour veterinary facility, and may also recommend referral to a specialty hospital where dialysis can be performed.  This procedure will help remove any remaining toxins from your pet’s blood as well as assist with treatment of kidney failure.   Because only a few hospitals offer dialysis in the United States, and because this treatment can be expensive, dialysis is often not pursued.


How can you prevent your pet from ingesting antifreeze?

  • Always keep your pet contained safely on your property – do not allow your pet to wander without supervision.  You can't control where antifreeze is spilled, cleaned up, or stored when off your property.
  • Keep pets away from areas containing these chemicals, such as garages and driveways where spills are most common
  • Store antifreeze containers in a place not accessible to pets or wildlife
  • Clean up antifreeze spills promptly
  • Check your car for antifreeze leaks regularly
  • Do not allow your pet to drink out of toilets containing antifreeze solutions


What about “pet friendly” antifreeze?

Most “pet friendly” antifreeze solutions contain propylene glycol instead of ethylene glycol.  Although propylene glycol can still be toxic to your pet, it does not cause kidney damage.  Ingestion of propylene glycol-containing chemicals should still prompt evaluation by a veterinarian.  Signs of toxicity include the following: severe sedation, walking as if drunk, seizures, tremors, panting, pale gums, and lethargy.

As always, be prepared – know where your closest emergency veterinary facility is located, just in case your pet needs care!

This blog post was written by the VMC’s Medical Director, Maureen Luschini, VMD, DACVECC