Poison Hemlock Toxic?

Updated 2026-03-06| 2 min read| 1,610 found this helpful

Conium maculatum

All parts of the plant are toxic, with highest alkaloid content in spring and during flowering.

Symptoms onset 10 minutes to 2 hours post-ingestion, with death possible from respiratory paralysis if untreated.

It closely resembles common edible umbelliferous plants, posing high accidental ingestion risk.

FAQ

Is Poison Hemlock toxic to Humans?

Agitation, tremors, drooling, muscle weakness, ataxia, initial CNS stimulation followed by depression, potential respiratory paralysis and death; may cause fetal birth defects if consumed during pregnancy (Severe)

Is Poison Hemlock toxic to Cats?

Agitation, tremors, drooling, diarrhea, paralysis, potential fatal respiratory failure (Severe)

Is Poison Hemlock toxic to Dogs?

Agitation, tremors, drooling, diarrhea, paralysis, possible death from respiratory arrest (Severe)

Is Poison Hemlock toxic to Horses?

Tremors, sudden stumbling, loss of consciousness, collapse, respiratory paralysis leading to death if untreated (Severe)

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Toxicity Details

Humans

Severe

Cats

Severe

Agitation, tremors, drooling, diarrhea, paralysis, potential fatal respiratory failure

Dogs

Severe

Agitation, tremors, drooling, diarrhea, paralysis, possible death from respiratory arrest

Horses

Severe

Tremors, sudden stumbling, loss of consciousness, collapse, respiratory paralysis leading to death if untreated

Toxicity Snapshot

Toxic PartsAll parts of the plant; highest toxicity in spring; alkaloid content decreases slowly when dried, so dried material remains toxic

Exposure RouteIngestion (primary exposure route), rare skin/mucous membrane irritation from contact with crushed plant material

Toxic CompoundsConiine; gamma-Conicein; Conhydrin; Pseudoconhydrin; Methylconiine; Other piperidine alkaloids

First Aid & Prevention

First 30 Minutes

• Induce vomiting only if ingestion occurred within 15 minutes and the patient is conscious and not seizing
• Administer activated charcoal to bind unabsorbed toxin in the gastrointestinal tract
• Keep the patient calm, ensure a clear airway, and monitor breathing closely while waiting for emergency care

Contact Vet Immediately

• Any confirmed or suspected Poison Hemlock ingestion, even if no symptoms are present
• Onset of any neurological or gastrointestinal symptoms including tremors, drooling, ataxia or diarrhea after plant exposure
• Any signs of respiratory distress, paralysis, or changes in consciousness

Prevention

• Remove all Poison Hemlock plants from areas accessible to pets, livestock and children
• Never forage wild umbelliferous plants unless you are 100% certain of their identity to avoid accidental ingestion
• Dispose of pulled Poison Hemlock safely, as dried plant material still retains residual toxicity

Treatment & Prognosis

• Perform gastrointestinal decontamination appropriate for the exposure timeline and patient status
• Provide symptomatic supportive care, including artificial respiratory support if needed, until the toxin is fully metabolized
• Continuously monitor neurological and respiratory function for at least 24 hours post-exposure

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Professional Toxicology

Scientific NameConium maculatum

AliasesPoison Parsley、Spotted Hemlock、Winter Fern、California Fern、Nebraska Fern、Deadly Hemlock

Toxicity Grade

HumansSevere

CatsSevere

DogsSevere

HorsesSevere

Target Organs

Central nervous systemRespiratory systemMusculoskeletal systemGastrointestinal tract

Mechanism of Action

• Piperidine alkaloids (primarily coniine) disrupt central nervous system function, causing initial stimulation followed by progressive depression

• Toxins block neuromuscular junctions, leading to muscle paralysis and eventual fatal respiratory failure

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: Most sensitive to toxicity; ingestion of fresh plant may cause skeletal birth defects and cleft palate in fetuses

Goats/Sheep: Sensitive to toxicity; fresh plant consumption may cause skeletal deformities and cleft palate in offspring

Pigs: Sensitive to toxicity; exposure may cause skeletal birth defects and cleft palate in fetuses

Juvenile animals of all species: More susceptible to toxicity than adult individuals of the same species

Confusion Risk

The following plants look similar and may be confused:

Fool's Parsley Aethusa cynapium

Toxic lookalike, shares similar umbelliferous leaf and flower structure with Poison Hemlock

Cow Parsley Anthriscus sylvestris

Non-toxic; key difference: produces black fruits, has no mouse urine-like odor when crushed

Wild Celery Apium graveolens

Non-toxic; key difference: broadly diamond to wedge-shaped leaves, dark brown fruits with yellow ribs

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Related Toxic Plants

Heracleum mantegazzianum

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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.

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