Hemlock Poisoning Clinical Presentation

Updated: Jan 29, 2021
  • Author: Daniel E Brooks, MD; Chief Editor: Michael A Miller, MD  more...
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In cases of plant toxicity, history may be obscure and ingested plants may not be available for identification.

History for poison hemlock may include the following:

  • Nausea and vomiting

  • Abdominal pain

  • Tachycardia

  • Tremor

  • Seizures (much more common with water hemlock)

  • Bradycardia (late)

  • Ascending paralysis (late)

  • Coma

  • Respiratory failure

History for water hemlock may include the following:

  • Gastrointestinal - Nausea and vomiting, excessive salivation, abdominal pain

  • Cardiac - Tachy/bradycardia, hypotension/hypertension, cardiac dysrhythmias/failure/arrest

  • Central nervous system - Delirium, convulsions, opisthotonus, hemiballismus, seizure (status epilepticus)



Poison hemlock: Signs of poison hemlock toxicity can be divided into an early stimulation phase and, in severe poisonings, a later depressant phase.

  • Emesis

  • Salivation

  • Mydriasis

  • Tachycardia, then bradycardia

  • Initial fasciculations, then flaccid paralysis

  • Hypoventilation, respiratory arrest

Water hemlock: Signs of water hemlock toxicity begin with GI symptoms, which are rapidly followed by CNS excitation.

  • Emesis

  • Mydriasis

  • Agitation

  • Delirium

  • Convulsions

  • Seizures

  • Coma



Hemlock plants may be intentionally ingested. However, most ingestions are unintentional.

Poison hemlock may be mistaken for wild carrots.

Water hemlock may be mistaken for wild parsnips or artichokes.

Birds ingesting hemlock during migratory flight may be reported to cause coturnism (human poisoning after eating quail).