Antifreeze is a common household chemical used in vehicles to regulate engine temperature. If ingested by a human, it is extremely toxic and potentially lethal, constituting a medical emergency requiring immediate attention. The compound is rapidly absorbed by the body, making timely medical intervention crucial for survival and long-term health outcomes. The severe danger lies not in the initial liquid itself, but in the highly destructive byproducts created as the body attempts to process the chemical.
Identifying the Deadly Ingredient
The primary toxic component in standard automotive antifreeze is Ethylene Glycol. This liquid is colorless, odorless, and possesses a distinctively sweet taste, which can attract children, pets, or individuals mistakenly looking for alcohol. Ingestion of as little as 1 to 2 milliliters per kilogram of body weight is considered a potentially lethal dose for an adult.
Some “safer” or environmentally friendly antifreeze products use Propylene Glycol as the main ingredient. Propylene Glycol is recognized as having a low toxicity and is even used in certain food, cosmetic, and pharmaceutical products. However, because Ethylene Glycol remains the standard and most dangerous variant, any ingestion of antifreeze should be treated as a severe poisoning event until proven otherwise.
How the Body Processes the Toxin
Ethylene Glycol itself does not cause the most severe damage; rather, it is the toxic metabolites produced when the liver processes it. The initial step involves an enzyme called alcohol dehydrogenase (ADH), which converts Ethylene Glycol into a series of increasingly harmful compounds.
The first conversion creates Glycoaldehyde, which is rapidly oxidized into Glycolic Acid. This Glycolic Acid accumulates in the bloodstream and is the primary cause of a severe condition known as metabolic acidosis, where the blood’s pH drops to dangerously low levels. The buildup of this acid leads to widespread cellular damage and is a major contributor to the later cardiopulmonary symptoms.
The final, highly destructive step involves the conversion of Glycolic Acid into Oxalic Acid. Oxalic Acid binds with calcium ions in the blood to form Calcium Oxalate crystals. These microscopic, insoluble crystals deposit throughout the body, primarily lodging in the kidneys, but also in the brain, heart, and lungs. The precipitation of these crystals in the renal tubules leads to physical obstruction and direct cellular injury, ultimately resulting in acute kidney failure.
Stages of Antifreeze Poisoning
The progression of Ethylene Glycol poisoning follows a predictable timeline, manifesting in three distinct stages of symptoms.
Neurological Phase
The first stage occurs within 30 minutes to 12 hours after ingestion. Symptoms are similar to alcohol intoxication, including dizziness, slurred speech, nausea, vomiting, and central nervous system (CNS) depression.
Cardiopulmonary Phase
The second stage begins approximately 12 to 36 hours post-ingestion. This phase is marked by the peak accumulation of Glycolic Acid, causing severe metabolic acidosis. The body attempts to compensate for this acid buildup by increasing the breathing rate, leading to hyperventilation, along with an elevated heart rate and signs of heart failure.
Renal Phase
The final and most devastating stage usually appears 24 to 72 hours after the exposure. The deposition of Calcium Oxalate crystals in the kidneys causes severe flank pain and a significant reduction in urine output. This leads to acute kidney injury, which can result in irreversible damage or death if not aggressively treated.
Life-Saving Medical Intervention
Immediate medical treatment is paramount, as the goal is to prevent the metabolism of Ethylene Glycol into its toxic acids.
Antidotes
The preferred and most effective medical antidote is Fomepizole, which acts as a potent inhibitor of the alcohol dehydrogenase (ADH) enzyme. By blocking this enzyme, Fomepizole stops the conversion of Ethylene Glycol, allowing the parent compound to be safely excreted by the kidneys.
An older, but still effective, alternative treatment is the administration of pharmaceutical-grade Ethanol (drinking alcohol). Ethanol works by saturating the ADH enzyme, competitively binding to it and preventing the enzyme from processing the Ethylene Glycol. While effective, Ethanol therapy is more complex to manage and less preferred than Fomepizole due to the need for constant monitoring.
Hemodialysis
In severe cases, or when a patient presents late with established metabolic acidosis or organ failure, hemodialysis is also a necessary intervention. This procedure filters the blood, effectively removing both the Ethylene Glycol and the highly toxic Glycolic and Oxalic Acid metabolites directly from the body. The most important action for anyone suspecting antifreeze ingestion is to call emergency medical services or Poison Control immediately.