Giant Hogweed Toxic?

Updated 2026-03-06| 5 min read| 4,619 found this helpful

Heracleum maximum

Giant Hogweed is confirmed toxic to cats, dogs, and horses per ASPCA research

Its core toxic active compound is furanocoumarins

Exposure leads to photosensitive dermatitis and potentially permanent ocular damage

FAQ

Is Giant Hogweed toxic to Humans?

Blistering, ulcerative exudative dermatitis triggered by photosensitization, eye irritation, and potential permanent vision impairment if sap contacts eyes (Moderate)

Is Giant Hogweed toxic to Cats?

Photosensitization leading to ulcerative and exudative skin lesions, eye irritation, and skin pain in sun-exposed areas (Moderate)

Is Giant Hogweed toxic to Dogs?

Ulcerative exudative dermatitis from photosensitivity, ocular redness, injury, and discomfort after contact or ingestion (Moderate)

Is Giant Hogweed toxic to Horses?

Severe photosensitive dermatitis with blistering lesions on exposed skin, ocular toxicity, and increased sensitivity to sunlight post-exposure (Moderate)

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Toxicity Details

Humans

Moderate

Blistering, ulcerative exudative dermatitis triggered by photosensitization, eye irritation, and potential permanent vision impairment if sap contacts eyes

Cats

Moderate

Photosensitization leading to ulcerative and exudative skin lesions, eye irritation, and skin pain in sun-exposed areas

Dogs

Moderate

Ulcerative exudative dermatitis from photosensitivity, ocular redness, injury, and discomfort after contact or ingestion

Horses

Moderate

Severe photosensitive dermatitis with blistering lesions on exposed skin, ocular toxicity, and increased sensitivity to sunlight post-exposure

Toxicity Snapshot

Toxic PartsAll plant parts are toxic, with highest concentration of harmful compounds present in the sap, leaves, and stems

Exposure RouteDirect skin/eye contact with plant sap, ingestion of plant material, or exposure of sap-contacted skin to UV sunlight

Toxic CompoundsFuranocoumarins

First Aid & Prevention

First 30 Minutes

• Move the affected individual/animal away from the plant and immediately out of direct sunlight
• Rinse all sap-contacted skin or eyes with cold running water for a minimum of 15 minutes
• Cover all exposed affected areas fully to block UV light until professional care is accessed
• Do not apply ointments, oils, or over-the-counter topical treatments before consulting a medical/vet professional

Contact Vet Immediately

• If your pet or horse has ingested any amount of Giant Hogweed tissue
• If you observe blistering, open skin lesions, eye redness, or squinting after potential exposure
• If the animal shows signs of pain, itchiness, or avoidance of sunlight after contact with the plant

Prevention

• Learn to identify Giant Hogweed and safely remove it from areas accessible to pets, livestock, and children
• Keep pets and horses on marked trails when hiking in regions where Giant Hogweed is known to be endemic
• Wear protective gloves, long sleeves, pants, and eye protection when handling unknown Apiaceae family plants

Treatment & Prognosis

• Provide supportive care including prescribed pain management and topical wound care for dermatitis lesions
• Restrict exposure to direct sunlight for 1 to 3 weeks post-exposure to prevent worsening of skin reactions
• Seek specialized ophthalmological care for any cases of eye exposure to prevent permanent vision damage

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Professional Toxicology

Scientific NameHeracleum maximum

AliasesCow Parsnip

Toxicity Grade

HumansModerate

CatsModerate

DogsModerate

HorsesModerate

Target Organs

SkinEyes

Mechanism of Action

• Furanocoumarins in plant tissue react with UV light when they come into contact with skin or eye tissue, triggering cellular damage, inflammation, and tissue necrosis that leads to visible clinical signs

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: At high risk of painful photosensitive dermatitis and eye damage if exposed to Giant Hogweed sap, with similar reaction severity to horses

Sheep: May develop mild to moderate blistering skin lesions on sun-exposed areas like the face and legs after contact with the plant

Goats: Lower risk of severe reactions compared to other livestock, but may still experience temporary skin irritation and photosensitivity after exposure

Confusion Risk

The following plants look similar and may be confused:

Queen Anne's Lace Daucus carota

Visually similar due to shared large white umbrella-shaped flower clusters; Queen Anne's Lace grows much shorter, has a distinct small dark purple flower in the center of its flower head, and does not produce toxic sap

Poison Hemlock Conium maculatum

Shares the Apiaceae family characteristic white umbrella flower clusters; Poison Hemlock has smooth, purple-spotted thin stems, while Giant Hogweed has thick, hairy green stems with purple blotches and grows 2 to 3 times taller on average

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Related Toxic Plants

Poison Hemlock

Conium maculatum

Severe toxicity, fatal if ingested by humans or any animal species

Water Hemlock

Cicuta maculata

Severe toxicity, highly neurotoxic and fatal even in very small ingestion doses

Wild Parsnip

Pastinaca sativa

Moderate toxicity, causes identical photosensitive dermatitis reactions as Giant Hogweed

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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.

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