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Hemlock Poisoning Clinical Presentation

  • Author: Daniel E Brooks, MD; Chief Editor: Asim Tarabar, MD  more...
Updated: Apr 21, 2015


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).

Contributor Information and Disclosures

Daniel E Brooks, MD Co-Medical Director, Banner Good Samaritan Poison and Drug Information Center, Department of Medical Toxicology, Banner Good Samaritan Medical Center

Daniel E Brooks, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology

Disclosure: Nothing to disclose.

Specialty Editor Board

John T VanDeVoort, PharmD Regional Director of Pharmacy, Sacred Heart and St Joseph's Hospitals

John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists

Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital

Disclosure: Nothing to disclose.

Additional Contributors

David A Peak, MD Associate Residency Director of Harvard Affiliated Emergency Medicine Residency; Attending Physician, Massachusetts General Hospital; Assistant Professor, Harvard Medical School

David A Peak, MD is a member of the following medical societies: American College of Emergency Physicians, Society for Academic Emergency Medicine, Undersea and Hyperbaric Medical Society, American Medical Association

Disclosure: Partner received salary from Pfizer for employment.


Michael Hodgman, MD Assistant Clinical Professor of Medicine, Department of Emergency Medicine, Bassett Healthcare

Michael Hodgman, MD is a member of the following medical societies: American College of Medical Toxicology, American College of Physicians, Medical Society of the State of New York, and Wilderness Medical Society

Disclosure: Nothing to disclose.

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Hemlock. Photo by Cornell University Poisonous Plants Informational Database
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