Winter is upon us. Snow, ice, and frigid temperatures mean that our car has to work a little harder to start and get warm. Part of making our car “winter ready” involves making sure that there is plenty of antifreeze in the radiator. This means that many pet owners will typically have a bottle of antifreeze handy, or a leaky radiator may leave a small puddle of it in your garage or driveway. According to the ASPCA Animal Poison Control Center database, the most common exposures with antifreeze occur with dogs and usually involve chewing on containers or lapping up spills. What is it about this common automobile fluid that makes it so toxic?

Ethylene Glycol

Ethylene glycol is the primary ingredient in most antifreeze products that makes it potentially fatal. In addition to being used in antifreeze, it can also be found in hydraulic brake fluid, snow globes, and industrial solvents. During the colder months, it can be a common reason for a trip to the veterinary emergency room.

While the ingestion of ethylene glycol alone can cause symptoms ranging from gastrointestinal upset, an increase in urination, and central nervous system depression, it is the way that the body metabolizes ethylene glycol that can result in acute kidney injury and subsequently cause death.

Dr. Amy Walsh is an emergency veterinarian at PetMed Emergency Center. She has treated a large number of antifreeze toxicities and holds a special interest in toxicology.

“Ethylene glycol by itself isn’t terribly toxic,” Walsh says. It causes gastrointestinal upset, central nervous system depression, and an increase in urination. It is the metabolites (or what the original chemical is turned into as the body tries to eliminate it) that causes acute kidney injury. The drugs we use for treatment actually prevent ethylene glycol from being metabolized. If the ethylene glycol can exit the body without being metabolized, the risk of acute kidney injury is greatly decreased.”

What Makes Antifreeze Appealing to Pets?

Ethylene glycol has a sweet scent and taste that is enticing to animals. Antifreeze that has either spilled or leaked from a vehicle may be accidently licked up by our pets for a variety of reasons.

“Animals who lack access to appropriate sources of clean water may investigate anything wet in an attempt to remain hydrated,” Walsh says. “Cats that walk through a puddle of antifreeze on the ground might groom it off themselves and ingest a quantity sufficient to induce toxicity.”

What are the Symptoms of Antifreeze Toxicity in Dogs and Cats?

“Initially, they can be pretty vague and non-specific,” Walsh says. “The animal might have some GI upset, seem sleepy, have some difficulty walking (a clumsy or “drunken” gait), or be observed drinking and urinating more than is usual.”

Left untreated, antifreeze toxicity will ultimately result in kidney failure. Signs of acute kidney failure are vomiting, low heart rate, decreased or absent urine output, vomiting, and lethargy.

How Much Antifreeze Does a Pet Need to Consume for it to be Life-Threatening?

Like any poison, the amount ingested can determine the treatment and the prognosis. Dr. Walsh notes that the level of toxicity depends on the concentration of the toxin in the product and the size and species of the patient. In feline patients especially, time is of the essence when it comes to treatment. In cats, if there are more than three to four hours between ingestion and treatment, the treatment will likely be ineffective.

“Most commercial antifreeze products contain between 95-97% ethylene glycol,” she says. “Other sources, like household paint, might contain less than 10-15%. For dogs, just under a teaspoon per kilogram of body weight induces toxicity. For a 55-pound dog, this would be about seven tablespoons. Cats are much more sensitive to the effects of the toxicity, and experience toxicity at doses as low as 1.5mL per kilogram. The average cat is 5kg, so roughly one and a half teaspoons.”

 If you think that your dog or cat has ingested antifreeze, the best thing to do is take them to a veterinarian as soon as possible.   A history, physical exam and bloodwork can help the doctor determine the next necessary course of action.

It is also a good idea to have the Animal Poison Control Center’s number on hand in the event of any toxicity:  888-426-4435