Ethylene glycol is extremely toxic when swallowed, and it can kill a healthy adult who drinks as little as a few ounces without treatment. The substance itself is not what does the damage: your liver converts it into a series of acids and crystals that wreck the kidneys, attack the brain, and can shut down multiple organs over the course of hours to days. What makes ethylene glycol especially dangerous is that it tastes sweet, has no strong odor, and is found in products stored in nearly every garage in cold climates.
Where You Run Into Ethylene Glycol
Most people encounter ethylene glycol as automotive antifreeze or engine coolant. It is also used in de-icing fluids for windshields and aircraft, and in some air-conditioning systems.1PubMed. Ethylene glycol, hazardous substance in the household But antifreeze is actually a small fraction of global ethylene glycol use. In 2013, about 86% of worldwide monoethylene glycol consumption went into producing polyethylene terephthalate (PET), the plastic used in clothing fibers, packaging film, and beverage bottles; only around 7.5% was used in antifreeze.2PLOS ONE. Clinical Features of Reported Ethylene Glycol Exposures in the United States It also serves as an industrial solvent and a precursor to polyester resins.3Academic Press. Ethylene Glycol: Industrial application and risk assessment
Poisoning almost always comes from drinking antifreeze, either intentionally or accidentally. The liquid is typically bright green or orange (thanks to added dye), but once mixed into a drink or consumed directly, its sweet taste provides little warning. Accidental ingestions tend to involve children or adults who mistake it for a beverage, while intentional ingestions include suicide attempts and, occasionally, homicides.
How the Body Turns It Into Poison
Ethylene glycol on its own is only mildly toxic. The real danger begins once the liver starts breaking it down. An enzyme called alcohol dehydrogenase converts ethylene glycol first into glycoaldehyde, which is then oxidized into glycolic acid, then glyoxylic acid, and finally oxalic acid.4PubMed. Current management of ethylene glycol poisoning Each of these metabolites causes its own problems, but two do most of the damage.
Glycolic acid is the main culprit behind the severe metabolic acidosis that characterizes ethylene glycol poisoning. In one study of poisoned patients, glycolate accounted for over 96% of the increased anion gap, the lab marker that signals acid is flooding the blood.5Acta Medica Scandinavica. Glycolate Causes the Acidosis in Ethylene Glycol Poisoning and is Effectively Removed by Hemodialysis This acid buildup can become life-threatening on its own, causing the body to struggle with every basic metabolic function.
Oxalic acid, the end product, combines with calcium in the blood to form calcium oxalate monohydrate crystals. These crystals deposit in the kidneys, where they attach to the lining of the kidney tubules and get pulled inside the cells. That triggers a cascade of damage: free radicals are produced, cell membranes break down, and the energy-producing structures inside kidney cells fail.6PubMed Central. Acute oxalate nephropathy caused by ethylene glycol poisoning Research in both animal models and cultured human kidney cells has shown that it is specifically these calcium oxalate crystals, not the dissolved oxalate ion or earlier metabolites, that cause the necrotic cell death leading to kidney failure.7PubMed. Are calcium oxalate crystals involved in the mechanism of acute renal failure in ethylene glycol poisoning?
Symptoms Progress in Stages
Ethylene glycol poisoning typically unfolds in three overlapping phases, though in practice they can blur together depending on how much was consumed and when treatment starts.8PubMed Central. Ethylene glycol poisoning
The first phase, appearing within the first several hours, is neurological. The person looks and acts intoxicated, much like someone who has had too much alcohol, with slurred speech, stumbling, nausea, and vomiting. Because ethylene glycol itself has some intoxicating effects before the toxic metabolites build up, early symptoms can be mistaken for ordinary drunkenness. This is one reason poisoning often goes unrecognized until it is well advanced.
The second phase, emerging roughly 12 to 24 hours after ingestion, involves the heart and lungs. Rapid breathing develops as the body tries to blow off the acid accumulating in the blood. Heart rate increases, and in severe cases, patients can develop respiratory distress, heart failure, or cardiovascular collapse.8PubMed Central. Ethylene glycol poisoning
The third phase, typically at 24 to 72 hours, is renal. The kidneys begin to fail as oxalate crystals accumulate and destroy tubule cells. Urine output drops. Without dialysis, this stage can be fatal or leave permanent kidney damage. Some patients need dialysis for weeks after a severe ingestion before kidney function recovers, and in a subset of cases it never fully does.
Diagnosing Ethylene Glycol Poisoning
Diagnosis is tricky because ethylene glycol does not show up on standard drug screens. Doctors typically rely on a combination of clinical suspicion and indirect lab findings. Two blood markers are particularly useful: the osmolal gap and the anion gap. Early after ingestion, unmetabolized ethylene glycol raises the osmolal gap (a measure of unaccounted-for dissolved particles in the blood). As metabolism proceeds and glycolic acid accumulates, the anion gap rises instead. In a retrospective study of over 340 patients with elevated osmolal gaps, all 77 who tested positive for a toxic alcohol had an elevated anion gap, an elevated osmolal gap, or both.9BioMed Central / PubMed Central. A retrospective analysis of glycol and toxic alcohol ingestion: utility of anion and osmolal gaps An osmolal gap above 50, in particular, was strongly suggestive of toxic alcohol presence.
A bedside clue that sometimes helps: most commercial antifreeze contains fluorescein, a dye added to help mechanics find radiator leaks. Shining an ultraviolet (Wood’s) lamp on a urine sample can reveal blue-green fluorescence. In one documented case, this urine fluorescence prompted clinicians to check for ethylene glycol, which came back at 133 mg/dL. Urinalysis in that patient also showed cigar-shaped and dumbbell-shaped calcium oxalate crystals, another classic but late-appearing sign.10BMJ Case Reports CP. Urine fluorescence in antifreeze poisoning The fluorescence test is not reliable on its own, though, since other substances can fluoresce and the dye may not always be present, so it should only be used alongside the clinical picture.
Definitive confirmation requires sending a blood sample for direct measurement of ethylene glycol and glycolic acid levels, usually by gas chromatography. Many hospitals do not run this test in-house, meaning results can take hours. That delay is why doctors often begin treatment based on clinical and lab suspicion alone rather than waiting for confirmation.
Treatment: Blocking the Enzyme
The core strategy is simple: if the liver’s conversion of ethylene glycol into toxic metabolites is the problem, block the enzyme responsible. Two drugs do this by occupying alcohol dehydrogenase so it cannot process ethylene glycol.
Fomepizole (brand name Antizol) is the preferred antidote in most settings. It is a potent inhibitor of alcohol dehydrogenase that prevents or sharply reduces the formation of toxic metabolites.11PubMed Central. Treatment of patients with ethylene glycol or methanol poisoning: focus on fomepizole A landmark trial published in the New England Journal of Medicine demonstrated that when fomepizole was given early in the course of poisoning, it prevented kidney injury by halting the metabolic cascade before glycolic acid and oxalate crystals could accumulate.12PubMed. Fomepizole for the Treatment of Ethylene Glycol Poisoning Fomepizole is administered intravenously, is easy to dose, and has relatively few side effects. Its main drawback is cost: it is expensive, and smaller or rural hospitals may not stock it.
Where fomepizole is unavailable, intravenous ethanol serves as a backup. Ethanol competes for alcohol dehydrogenase and actually has a higher affinity for the enzyme than ethylene glycol does, so flooding the system with ethanol effectively shuts down toxic metabolism. The trade-offs, however, are significant. Ethanol therapy requires intensive care monitoring with blood levels checked every few hours. It can cause its own problems, including low blood sugar, liver stress, and worsened brain depression on top of the ethylene glycol intoxication, making it harder for clinicians to track the patient’s actual clinical course.13PubMed Central. Oral Ethanol Treatment for Ethylene Glycol Intoxication
When Dialysis Becomes Necessary
Fomepizole or ethanol can stop new toxins from being produced, but they do nothing about glycolic acid and ethylene glycol already circulating in the blood. Hemodialysis physically removes both. A systematic review by an international toxicology workgroup found that ethylene glycol and glycolate are both cleared effectively by intermittent hemodialysis.14PubMed Central. Extracorporeal treatment for ethylene glycol poisoning: systematic review and recommendations from the EXTRIP workgroup
The workgroup’s guidelines give a sense of how decisions are made. When fomepizole is being used, they suggest adding dialysis if the ethylene glycol level is very high or the osmolal gap exceeds 50. When ethanol is the antidote instead, the recommendation for dialysis at those same thresholds is stronger, because ethanol’s side effects make prolonged treatment riskier. Dialysis is recommended outright if the patient shows severe signs like coma, seizures, or acute kidney injury.14PubMed Central. Extracorporeal treatment for ethylene glycol poisoning: systematic review and recommendations from the EXTRIP workgroup In practice, many seriously poisoned patients receive both an antidote and dialysis simultaneously.
Delayed Neurological Problems
Even patients who survive the acute phase and recover kidney function sometimes develop neurological complications days or weeks later. The most commonly reported delayed effect is cranial nerve dysfunction, particularly involving the facial nerve (cranial nerve VII), which can cause one-sided facial weakness or paralysis. These deficits have appeared anywhere from 5 to 20 days after the poisoning event. Rarer delayed effects include Parkinsonism and cerebral swelling.15PubMed. Delayed neurological sequelae from ethylene glycol, diethylene glycol and methanol poisonings The mechanism behind these late-onset symptoms is not fully understood, but researchers suspect residual metabolite injury to nerve tissue that continues even after the acute metabolic crisis resolves. Some patients recover from these neurological effects over months; others do not.
Pets Are at Even Greater Risk
Ethylene glycol poisoning is a well-known veterinary emergency, and the outcomes are grimmer than in humans, partly because pets often present late. Cats and small dogs can be fatally poisoned by lapping up a puddle of leaked coolant from a garage floor. A retrospective review of companion animals hospitalized for ethylene glycol poisoning at a Canadian veterinary teaching hospital over 17 years found survival-to-discharge rates of 33% for dogs and 0% for cats.16The Canadian Veterinary Journal. A retrospective case series of companion animals hospitalized for ethylene glycol poisoning at a Canadian veterinary teaching hospital Most animals in that study were brought in more than eight hours after signs began, by which point significant metabolism had already occurred. Cats appear especially vulnerable because they lack some of the metabolic capacity that gives dogs a slightly wider window for treatment. Fomepizole (marketed as 4-methylpyrazole in veterinary medicine) was the most commonly used antidote alongside IV fluids in the cases reviewed.
Propylene Glycol as a Safer Alternative
One question that comes up often is why ethylene glycol is still used in consumer products when safer alternatives exist. Propylene glycol, a closely related compound, can function as an antifreeze and is far less toxic. A comprehensive review comparing the two found that ethylene glycol exceeds propylene glycol in lethality, acute toxic effects, and reproductive, developmental, and kidney toxicity.17PubMed. A review of the comparative mammalian toxicity of ethylene glycol and propylene glycol Propylene glycol is considered safe enough to be used as a food additive and in pharmaceutical preparations.
Despite this, ethylene glycol remains the standard in automotive coolant for practical reasons: it has a lower freezing point, better heat-transfer properties, and is cheaper to produce at scale. “Pet-safe” or “low-tox” antifreeze formulations that use propylene glycol are available but carry a price premium and are not as widely stocked. They are worth seeking out if you have pets or small children.
Why Bittering Agents Have Not Solved the Problem
Several U.S. states and other jurisdictions have passed laws requiring manufacturers to add denatonium benzoate, an intensely bitter substance, to antifreeze. The logic is straightforward: make it taste terrible and fewer people will swallow it. The evidence, however, is discouraging. A study analyzing pediatric antifreeze ingestions in Oregon and California found that the frequency of ingestions did not change after bittering mandates took effect. The volume children swallowed, the severity of symptoms, and rates of hospitalization, critical care, dialysis, and intubation were all statistically no different between bittered and non-bittered groups.18PubMed. The impact of bittering agents on pediatric ingestions of antifreeze
Suicidal ingestions were similarly unaffected. A parallel analysis of intentional antifreeze ingestions found no change in frequency, volume consumed, or outcomes after bittering was introduced.19PubMed. The impact of bittering agents on suicidal ingestions of antifreeze This makes sense in retrospect: a person determined to harm themselves is unlikely to be deterred by a bad taste, and young children may not respond to bitterness the way adults expect. The result is that bittering agents provide a false sense of security. Safe storage, locked cabinets, and prompt cleanup of spills remain the only reliably effective prevention strategies.
Forensic Challenges After Fatal Poisoning
Ethylene glycol poisoning is an uncommon but real forensic concern, and confirming it after death can be difficult. Autopsy findings are nonspecific, and standard postmortem toxicology panels do not include ethylene glycol, meaning the poisoning can go undetected unless the pathologist specifically orders testing for it.20Toxicologie Analytique et Clinique. Deaths related to acute ethylene glycol ingestion: A not-so-simple post-mortem situation Even when targeted testing is performed, the results require careful interpretation. In a study of 12 medical examiner cases where ethylene glycol poisoning was the cause of death, postmortem blood ethylene glycol concentrations ranged enormously, from 58 to 7,790 mg/L, while glycolic acid levels clustered more tightly between 810 and 1,770 mg/L. The two measurements correlated poorly with each other in postmortem samples, which means a low ethylene glycol level in the blood does not rule out lethal poisoning, since most of the parent compound may have already been metabolized.21PubMed. Ethylene glycol and glycolic acid in postmortem blood from fatal poisonings Calcium oxalate crystals in kidney tissue were a consistent finding across cases and remain one of the most reliable postmortem indicators.
Environmental Runoff From Deicing
Beyond human and animal health, ethylene glycol raises environmental concerns. Airports use large volumes of glycol-based deicing fluids, and runoff from these operations can enter nearby waterways. When glycol reaches surface water, aquatic bacteria break it down and consume oxygen in the process, which can deplete dissolved oxygen to levels that stress or kill fish and invertebrates. Laboratory studies on aquatic organisms have tested the toxicity of both pure and formulated glycol products. Pure ethylene glycol was toxic to water fleas at concentrations above about 34,000 mg/L over 48 hours, but formulated deicing products were far more toxic, killing the same organisms at around 13,000 mg/L, likely because of additives in the commercial mixtures.22Environmental Toxicology and Chemistry. Comparative toxicity of formulated glycol deicers and pure ethylene and propylene glycol to Ceriodaphnia dubia and Pimephales promelas These concentrations are high compared to what typically appears in streams, but localized runoff near airports or industrial facilities can spike to problematic levels, especially in cold weather when deicing is heaviest and water flows are low.