Ethylene Glycol (Antifreeze) Poisoning

What to do right now

1. Call 911 or your local emergency number if the person is drowsy, confused, breathing fast, having a seizure or unresponsive.
2. If they are alert, call Poison Control at 1-800-222-1222 in the US. Experts answer 24 hours a day, free and confidential.
3. Do not wait for symptoms. The dangerous phase starts hours later. By then much of the damage is under way.
4. Do not make them vomit, and do not give activated charcoal, which does not bind ethylene glycol.
5. Bring the container, or a photo of the label, so staff know the product and its strength.
6. If it is on the skin, remove soaked clothing and wash with soap and water. If it is in the eyes, rinse with lukewarm running water for 15 minutes.

How can you get ethylene glycol poisoning?

Ethylene glycol is a colorless, odorless, sweet-tasting liquid. That sweet taste is what makes it dangerous. It is found in:

• car antifreeze and engine coolant (the most common source)
• some brake and hydraulic fluids
• windshield de-icers and some windshield washer fluids
• some paints, solvents, inks and heat-transfer fluids
• some fake or contaminated medicines and syrups, which have caused mass poisonings in several countries

Exposure happens in three main ways:

• Accidental swallowing: a child drinks coolant from a soda bottle or an open container in a garage. Pets are also poisoned by drinking puddles of leaked coolant.
• Intentional swallowing: as self-harm, or by someone who drinks it as a substitute for alcohol.
• Contaminated products: medicines, toothpaste or drinks made with industrial glycols instead of pharmaceutical-grade ingredients.

Breathing in vapor or getting it on the skin rarely causes poisoning. Ethylene glycol does not evaporate easily, and very little passes through intact skin. Low-level workplace exposure can irritate the eyes, nose and throat, but serious poisoning almost always means swallowing it.

Small amounts are dangerous. A few mouthfuls can seriously poison a child, and roughly 100 ml (about 3 ounces) can kill an adult without treatment.

How ethylene glycol harms the body

Ethylene glycol itself acts like alcohol on the brain. The real damage comes from what the liver turns it into. An enzyme called alcohol dehydrogenase converts it, step by step, into:

• glycolic acid, which builds up in the blood and causes severe metabolic acidosis, meaning the blood becomes too acidic
• oxalic acid, which binds calcium to form sharp calcium oxalate crystals. These lodge in the kidneys and cause acute kidney injury. Binding calcium can also cause low blood calcium, with muscle spasms and heart rhythm problems

The antidote works by blocking that first enzyme, so the ethylene glycol is never turned into toxic acids and is instead passed out unchanged in the urine.

Ethylene glycol poisoning symptoms by stage

Symptoms come in three overlapping stages. Timing varies with the dose and is delayed if the person also drank alcohol, because alcohol slows the conversion.

Other signs of antifreeze poisoning include:

• confusion and agitation without a smell of alcohol
• belly pain and repeated vomiting
• muscle twitching or spasms from low calcium
• seizures
• weeks later, in some survivors, damage to cranial nerves causing facial weakness, hearing or vision problems

Some antifreeze contains a fluorescent dye, so a doctor may check the urine under an ultraviolet lamp. This test is unreliable, and a negative result does not rule out poisoning.

Symptoms of low-dose or repeated exposure

Swallowing small amounts repeatedly over time is unusual, but it has been reported, including in deliberate poisonings. It can cause repeated episodes of nausea, vomiting, unsteadiness and confusion, followed by gradually worsening kidney function. Long-term breathing of heated vapor at work can irritate the airways and cause headaches. Anyone with unexplained kidney problems and possible ongoing exposure should tell their doctor, who can check the blood acid level, the osmolal gap and urine crystals.

How doctors diagnose it

Diagnosis rests on the story of exposure plus blood tests. Doctors look for:

• Metabolic acidosis with a high anion gap: too much acid in the blood from an unmeasured source.
• A raised osmolal gap: a sign of an unmeasured alcohol in the blood, most obvious early on. It falls as ethylene glycol is converted, so a normal gap later does not rule it out.
• Ethylene glycol blood level: the confirming test, though not every hospital can run it quickly.
• Kidney function and calcium: rising creatinine and low calcium.
• Urine: calcium oxalate crystals under the microscope.

Doctors also check for alcohol, acetaminophen and other substances, because many people swallow more than one thing. Treatment is usually started on suspicion, before results return.

Antifreeze poisoning treatment

Antidote

Fomepizole is the first-choice antidote. It blocks alcohol dehydrogenase so ethylene glycol cannot be converted into toxic acids. It is given through a drip and works best before acidosis and kidney damage set in. Where fomepizole is not available, doctors give ethanol (medical alcohol) through a drip or by mouth, which competes for the same enzyme. Ethanol needs close monitoring and causes intoxication.

Hemodialysis

Dialysis filters ethylene glycol and its toxic acids out of the blood, corrects the acidosis and supports the kidneys. It is used when there is severe acidosis, kidney failure, a high ethylene glycol level, or the person is very unwell.

Supportive care

• Intravenous fluids, and sodium bicarbonate to reduce acidity
• Breathing support in intensive care if needed
• Treatment of seizures and low calcium
• Vitamins thiamine and pyridoxine (B6), which help shift metabolism toward less harmful products

Outlook

When the antidote is started early, before significant acidosis, most people recover fully. The later treatment starts, the higher the risk of permanent kidney damage or death. Kidney function often recovers over weeks to months, though some people need dialysis for a while, and a few long term. Anyone who swallowed it on purpose should receive mental health support before leaving the hospital.

Preventing antifreeze poisoning

• Store antifreeze and coolant in the original container, locked away from children and pets.
• Never pour it into drink bottles.
• Clean up spills and leaks straight away, and dispose of old coolant at a recycling center.
• Choose products that contain a bittering agent (denatonium benzoate). Many US states require it in antifreeze.
• Consider propylene glycol-based antifreeze, which is much less toxic, though not completely safe.
• Only buy medicines and syrups from licensed sources.

Frequently asked questions

What are the first symptoms of antifreeze poisoning?

In the first few hours, the person usually looks drunk: slurred speech, unsteadiness, nausea, vomiting and drowsiness, without a smell of alcohol. Fast, deep breathing, a racing heart and seizures follow 12 to 24 hours later, and kidney failure after 24 to 72 hours.

How is ethylene glycol poisoning treated?

Hospitals give the antidote fomepizole, or ethanol where fomepizole is unavailable, to stop the body turning ethylene glycol into toxic acids. Hemodialysis removes the poison and acids. Fluids, sodium bicarbonate, vitamins and intensive care support the person while the body clears it.

How much antifreeze is dangerous?

Very little. A single mouthful can be dangerous for a child, and about 100 ml (3 ounces) can kill an adult without treatment. Any amount swallowed needs a call to Poison Control at 1-800-222-1222 (US) or emergency care, even without symptoms.

Can you get ethylene glycol poisoning from breathing fumes or skin contact?

Serious poisoning from fumes or skin contact is rare. Ethylene glycol evaporates slowly and passes poorly through intact skin. Heated vapor can irritate the eyes and airways. Wash skin with soap and water and rinse eyes for 15 minutes. Poisoning almost always comes from swallowing it.

Can someone survive ethylene glycol poisoning?

Yes. With prompt antidote treatment and dialysis, most people survive, and many recover full kidney function. The outlook worsens the longer treatment is delayed, which is why anyone who may have swallowed antifreeze should go to the ER immediately rather than waiting for symptoms.

Why is antifreeze poisoning so common in pets?

Antifreeze tastes sweet, so dogs and cats lap it from leaks and puddles. A small amount can kill a cat. Pets need veterinary treatment within hours. Clean leaks promptly and use antifreeze with a bittering agent or a propylene glycol formula.