Leek Toxic?

Updated 2026-03-06| 4 min read| 4,487 found this helpful

Leek is confirmed toxic to cats, dogs, and horses, with all plant parts carrying toxicity risk even when cooked.

Its primary toxic compound is N-propyl disulfide, which causes oxidative damage to red blood cells in vulnerable species.

Ingestion may lead to life-threatening hemolytic anemia, requiring immediate veterinary intervention for affected animals.

FAQ

Is Leek toxic to Humans?

Non-toxic in standard culinary serving sizes; excessive intake may cause mild gastrointestinal upset and allergic reactions in sensitive individuals. (Non-toxic)

Is Leek toxic to Cats?

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, potential organ damage in severe cases. (High)

Is Leek toxic to Dogs?

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, increased risk of complications with large ingestions. (Moderate)

Is Leek toxic to Horses?

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, reduced exercise tolerance post exposure. (Moderate)

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Toxicity Details

Humans

Non-toxic

Non-toxic in standard culinary serving sizes; excessive intake may cause mild gastrointestinal upset and allergic reactions in sensitive individuals.

Cats

High

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, potential organ damage in severe cases.

Dogs

Moderate

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, increased risk of complications with large ingestions.

Horses

Moderate

Vomiting, hemolytic anemia (Heinz body anemia), blood in urine, weakness, elevated heart rate, panting, reduced exercise tolerance post exposure.

Toxicity Snapshot

Toxic PartsAll plant parts, including bulbs, stems, leaves, and juice, are toxic both raw and cooked.

Exposure RouteIngestion is the primary confirmed toxic exposure route; skin contact may cause mild localized irritation in sensitive individuals.

Toxic CompoundsN-propyl disulfide

First Aid & Prevention

First 30 Minutes

• Remove all remaining leek material from the animal's mouth and immediate environment to stop further ingestion.
• If ingestion occurred within the past 2 hours, contact a vet immediately to confirm if inducing vomiting is appropriate.
• Collect a sample of the ingested plant to share with veterinary staff for accurate identification.

Contact Vet Immediately

• If you confirm or suspect a cat, dog, or horse has ingested any quantity of leek, even if no symptoms are visible.
• If you observe symptoms including vomiting, blood in urine, weakness, or abnormal breathing after potential exposure.
• If you are unsure if the plant ingested is leek or another toxic Allium species.

Prevention

• Keep leek and related Allium plants (onion, garlic, chives) out of reach of companion animals.
• Do not feed table scraps containing leek or related Allium ingredients to cats, dogs, or horses.
• Regularly clear horse pastures of wild growing Allium ampeloprasum and related toxic species.

Treatment & Prognosis

• Veterinary administration of activated charcoal to reduce absorption of toxic compounds for recent ingestions.
• Supportive care including intravenous fluids, blood transfusions, and oxygen therapy for severe anemia cases.
• Monitoring of red blood cell count, kidney function, and oxygen levels for 24 to 72 hours post exposure.

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Professional Toxicology

Scientific NameAllium ampeloprasum

AliasesElephant Garlic

Toxicity Grade

HumansNon-toxic

CatsHigh

DogsModerate

HorsesModerate

Target Organs

Red blood cellsKidneysCardiovascular system

Mechanism of Action

• N-propyl disulfide induces oxidative damage to the membranes of red blood cells.

• Oxidative stress causes Heinz body formation and premature breakdown of red blood cells (hemolysis).

• Reduced red blood cell count leads to insufficient oxygen delivery to bodily organs and tissues.

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: Moderate toxicity; ingestion of large quantities of leek may cause hemolytic anemia, reduced milk production, and weakness.

Sheep: Low to moderate toxicity; more resistant to Allium toxins than cats or dogs, but may develop anemia after sustained high intake.

Rabbits: High toxicity; ingestion may lead to hemolytic anemia, gastrointestinal stasis, and potentially fatal complications.

Confusion Risk

The following plants look similar and may be confused:

Common Onion Allium cepa

Visually similar to leek, but has a distinct rounded bulb at the base compared to the long, cylindrical non-bulbous stem of leek; both are toxic to cats, dogs, and horses.

True Garlic Allium sativum

Often confused with the elephant garlic variant of leek; true garlic has small, multiple segmented cloves, while elephant garlic has much larger, fewer cloves and a milder flavor.

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Related Toxic Plants

Common Onion

Allium cepa

High toxicity for cats, dogs, and horses

Garlic

Allium sativum

High toxicity for cats, dogs, and horses

Chives

Allium schoenoprasum

Moderate toxicity for cats, dogs, and horses

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Data Sources

1. ASPCA Animal Poison Control

This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.