Pet Safety / Compounds / Hydrogen cyanide

Is Hydrogen cyanide safe for dogs and cats?

High risk for pets

Dogs may be exposed to HCN from: (1) house fires — HCN is a major cause of smoke inhalation fatalities in pets; (2) ingestion of stone fruit seeds or apple seeds (amygdalin hydrolysis); (3) certain plant exposures (elderberries, Prunus spp. leaves and bark, cassava). Signs of acute CN poisoning: sudden collapse, severe dyspnea, seizures, bright-red venous blood (high venous O₂ saturation because tissues cannot extract O₂), cardiac arrest. Emergency treatment: fresh air + 100% O₂ + IV hydroxocobalamin (where veterinary form available). Small dogs are at greater risk from plant sources due to lower lethal dose threshold.

What is hydrogen cyanide?

The IUPAC name is formonitrile.

Also known as: formonitrile, hydrocyanic acid, Prussic acid, Blausaeure.

IUPAC name
formonitrile
CAS number
74-90-8
Molecular formula
CHN
Molecular weight
27.025 g/mol
SMILES
C#N
PubChem CID
768

Risk for dogs

High risk

Dogs may be exposed to HCN from: (1) house fires — HCN is a major cause of smoke inhalation fatalities in pets; (2) ingestion of stone fruit seeds or apple seeds (amygdalin hydrolysis); (3) certain plant exposures (elderberries, Prunus spp. leaves and bark, cassava). Signs of acute CN poisoning: sudden collapse, severe dyspnea, seizures, bright-red venous blood (high venous O₂ saturation because tissues cannot extract O₂), cardiac arrest. Emergency treatment: fresh air + 100% O₂ + IV hydroxocobalamin (where veterinary form available). Small dogs are at greater risk from plant sources due to lower lethal dose threshold.

Risk for cats

High risk

Cats are susceptible to HCN from the same sources as dogs. Cats that hunt or are offered raw diets may encounter stone-fruit scraps; a single bitter almond or multiple apple seeds could potentially deliver a toxic CN dose to a small cat. House fires present the highest HCN risk — cats may be less likely to escape burning structures. Clinical signs and treatment are identical to dogs. Veterinary first responders at fire scenes should administer O₂ immediately to any smoke-exposed pet and monitor for delayed CN toxicity.

Regulatory consensus

7 regulatory and scientific bodies have classified Hydrogen cyanide. The classifications differ — that's the data.

AgencyYearClassificationNotes
IARC—Not classified as a carcinogen
US EPA—Not classified as a carcinogen
EPA CTX / Skin-Eye—Eye Irritation: Serious eye damage/eye irritation - Category 2 (score: high)
EPA CTX / Skin-Eye—Eye Irritation: Category 2A-2B (score: high)
EPA CTX / Skin-Eye—Eye Irritation: Category 6.4A (Category 2A) (score: high)
EPA CTX / Skin-Eye—Skin Irritation: Category 6.3A (Category 2) (score: high)
EPA CTX / Skin-Eye—Skin Sensitization: Category 6.5B (Category 1) (score: moderate)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where pets encounter hydrogen cyanide

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Hydrogen cyanide:

  • Process redesign to avoid hazardous intermediates
    Trade-offs: May require significant R&D investment. Not always feasible.
    Relative cost: 1.2-2×

Frequently asked questions

Is hydrogen cyanide safe for pets?

Dogs may be exposed to HCN from: (1) house fires — HCN is a major cause of smoke inhalation fatalities in pets; (2) ingestion of stone fruit seeds or apple seeds (amygdalin hydrolysis); (3) certain plant exposures (elderberries, Prunus spp. leaves and bark, cassava). Signs of acute CN poisoning: sudden collapse, severe dyspnea, seizures, bright-red venous blood (high venous O₂ saturation because tissues cannot extract O₂), cardiac arrest. Emergency treatment: fresh air + 100% O₂ + IV hydroxocobalamin (where veterinary form available). Small dogs are at greater risk from plant sources due to lower lethal dose threshold.

What products contain hydrogen cyanide?

Hydrogen cyanide appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments).

Why do regulators disagree about hydrogen cyanide?

Hydrogen cyanide has been classified by 7 agencies including IARC, US EPA, EPA CTX / Skin-Eye, EPA CTX / Skin-Eye, EPA CTX / Skin-Eye, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Hydrogen cyanide in the pets app

Look up products containing hydrogen cyanide, compare to alternatives, and explore the full data record.

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Sources (4)
  1. ATSDR Toxicological Profile for Cyanide (2006) — report
  2. CDC Emergency Preparedness and Response: Cyanide — Medical Management Guidelines (2018) — report
  3. NIOSH Pocket Guide to Chemical Hazards: Hydrogen Cyanide (2019) — regulatory
  4. ASPCA Animal Poison Control Center: Cyanide Toxicosis in Companion Animals (2020) — report

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →