Black Walnut Toxic?

Updated 2026-03-06| 3 min read| 2,612 found this helpful

Non-toxic to cats, but confirmed toxic to dogs and horses per ASPCA data

Moldy nut hulls, wood shavings and sawdust are the highest-risk toxic parts

Canine mold-related toxicity has 15 minute to 3 hour onset, with recovery in 12-48 hours

FAQ

Is Black Walnut toxic to Humans?

No confirmed human toxicity cases reported; large ingestion of green hulls may cause mild gastrointestinal irritation (Non-toxic)

Is Black Walnut toxic to Cats?

No known toxicity, no associated adverse symptoms recorded (Non-toxic)

Is Black Walnut toxic to Dogs?

Salivation, vomiting, weakness, ataxia, hyperthermia, tremors, tonic-clonic seizures, hyperesthesia, incoordination from shaving ingestion (Moderate)

Is Black Walnut toxic to Horses?

Laminitis, colic, gastrointestinal irritation from large intake of green hulls or leaves (Moderate)

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Toxicity Details

Humans

Non-toxic

No confirmed human toxicity cases reported; large ingestion of green hulls may cause mild gastrointestinal irritation

Cats

Non-toxic

No known toxicity, no associated adverse symptoms recorded

Dogs

Moderate

Salivation, vomiting, weakness, ataxia, hyperthermia, tremors, tonic-clonic seizures, hyperesthesia, incoordination from shaving ingestion

Horses

Moderate

Laminitis, colic, gastrointestinal irritation from large intake of green hulls or leaves

Toxicity Snapshot

Toxic PartsFruit hulls (highly toxic if colonized by toxin-producing fungi), heartwood (sawdust and shavings)

Exposure RouteIngestion of moldy nuts/hulls, leaves or sawdust; skin/respiratory exposure to sawdust; contact with black walnut shaving bedding

Toxic CompoundsPenitrem A (tremorgenic mycotoxin); Roquefortine C (biomarker for Penitrem A exposure); Ellagitannins (tannins found in leaves and fruit hulls)

First Aid & Prevention

First 30 Minutes

• Remove all remaining black walnut material or contaminated bedding from the animal's environment immediately
• Induce vomiting only if ingestion occurred <2 hours prior and the animal is fully conscious
• Administer activated charcoal if available to reduce toxin absorption, unless the animal is seizuring

Contact Vet Immediately

• Dog shows tremors, seizures, incoordination or vomiting after exposure to black walnut material
• Horse shows signs of laminitis, colic or unexplained lameness after exposure to black walnut shavings
• Any animal displays persistent abnormal symptoms within 6 hours of suspected exposure

Prevention

• Never use black walnut shavings as bedding for dogs or horses
• Dispose of moldy black walnut hulls and nuts away from pet and livestock access areas
• Regularly inspect pastures, enclosures and bedding for black walnut plant material

Treatment & Prognosis

• Perform decontamination (emesis, activated charcoal administration) as clinically appropriate
• Administer Diazepam or Propofol to dogs experiencing seizures or severe tremors
• Prescribe non-steroidal anti-inflammatory drugs for horses presenting with laminitis
• Provide supportive care (fluid therapy, temperature regulation) until symptoms resolve

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Professional Toxicology

Scientific NameJuglans nigra

AliasesAmerican Walnut、Eastern Black Walnut

Toxicity Grade

HumansNon-toxic

CatsNon-toxic

DogsModerate

HorsesModerate

Target Organs

Gastrointestinal tractNervous systemHoof laminae (horses)Musculoskeletal system

Mechanism of Action

• Tremorgenic mycotoxins from mold growing on hulls/nuts cause neurological dysfunction in dogs

• Ellagitannins in leaves and green hulls trigger gastrointestinal irritation if ingested in large volumes

• Compounds in black walnut heartwood extracts disrupt hoof vascular function to cause laminitis in horses

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Birds: Severe toxicity, ingestion of toxin-containing black walnut parts can cause fatal poisoning

Ruminant livestock (cattle, sheep): Limited data, but ingestion of moldy hulls may cause gastrointestinal irritation and neurological symptoms

Confusion Risk

The following plants look similar and may be confused:

Common Walnut Juglans regia

Closely related Juglans species with near-identical leaf and nut morphology; carries similar mold-related toxicity risks for animals

Butternut Juglans cinerea

North American Juglans species with visually similar leaves and green fruit hulls, often mistaken for immature black walnut

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Related Toxic Plants

Common Walnut

Juglans regia

Low to Moderate toxicity, moldy hulls pose tremor risk for dogs

Bitternut Hickory

Carya cordiformis

Low toxicity, unripe nuts cause gastrointestinal irritation in animals

Pecan

Carya illinoinensis

Low toxicity, moldy nuts carry tremorgenic mycotoxin risk for dogs

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Data Sources

1. ASPCA Animal Poison Control

2. CliniTox (Universität Zürich)

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