Ethylene Glycol (see also Antifreeze under Household)

How Much Is Dangerous

As little as one to two teaspoons can be lethal to an average cat, regardless of which specific product it originated from — the danger lies in the chemical itself, not in whatever the product happens to be labeled or marketed as, meaning a "brake fluid" or "hydraulic fluid" spill deserves exactly the same emergency response as a recognized antifreeze spill.

Symptoms

• Stage 1 (30 minutes to 12 hours after ingestion): appears drunk or uncoordinated, vomiting, excessive thirst and urination, seizures possible — reflecting the direct CNS-depressant effect of the unmetabolized chemical, similar to alcohol intoxication
• Stage 2 (12–24 hours after ingestion): apparent improvement as acute neurological signs subside — this is deceptive, not genuine recovery, and represents the transition into the phase where toxic metabolites are actively accumulating
• Stage 3 (24–72 hours after ingestion): established kidney failure — lethargy, vomiting, reduced or absent urine output, seizures, coma

Time to Symptoms

Initial neurological signs within 30 minutes to a few hours of ingestion; established, often fatal kidney failure develops within 24–72 hours, following the identical timeline described for antifreeze specifically since the underlying chemical and mechanism are the same.

First Aid Steps

• Treat as an extreme emergency regardless of which specific product the ethylene glycol came from — go to an emergency animal hospital immediately, including overnight if needed
• Do not wait for symptoms — early treatment, before kidney damage has begun, is genuinely what saves lives with this specific poison, more so than with almost anything else on this list
• If you find any unlabeled or unidentified automotive/industrial fluid spill with a cat nearby, treat it as a potential ethylene glycol exposure until proven otherwise, given the severity if it does turn out to be the case

What Not To Do

• Do not assume only products specifically branded or labeled as "antifreeze" carry this risk — check the ingredient list of any automotive, hydraulic, or de-icing fluid for ethylene glycol specifically, since the branding or product category name doesn't reliably indicate the presence or absence of this chemical
• Do not wait to see if the cat seems okay during the deceptive stage 2 apparent-improvement window described above

Veterinary Treatment

Time-critical antidote therapy (fomepizole or ethanol) if given before significant metabolism has occurred, ideally within a few hours of ingestion; supportive care and a substantially poorer prognosis once established kidney damage has set in, following the identical treatment approach and timeline described for antifreeze specifically.

Toxic Compound

See the main "Antifreeze (Ethylene Glycol)" entry in the Household category for the full mechanism detail — this entry specifically covers ethylene glycol encountered outside of antifreeze products, such as some hydraulic fluids, brake fluid, and certain de-icing formulations, all of which share the identical toxic mechanism (metabolism into calcium-oxalate-forming compounds that destroy kidney tissue) and carry the identical, extreme level of urgency regardless of which specific product the chemical came from.