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Michael R Lee1, Estela Dukan2, Iain Milne3

Author Affiliations: 

1Emeritus Professor of Clinical Pharmacology and Therapeutics, University of Edinburgh, Edinburgh, UK; 2Librarian, Royal College of Physicians of Edinburgh, Edinburgh, UK; 3Head of Heritage, Royal College of Physicians of Edinburgh, Edinburgh, UK

Correspondence to: 

Michael R Lee, 112 Polwarth Terrace, Merchiston, Edinburgh EH11 1NN, UK

Journal Issue: 
Volume 50: Issue 1: 2020
Cite paper as: 
J R Coll Physicians Edinb 2020; 50: 80–6



Although we are familiar with common British plants that are poisonous, such as Atropa belladonna (deadly nightshade) and Aconitum napellus (monkshood), the two most poisonous plants in the British Flora are Oenanthe crocata (dead man’s fingers) and Cicuta virosa (cowbane). In recent years their poisons have been shown to be polyacetylenes (n-C2H2). The plants closely resemble two of the most common plants in the family Apiaceae (Umbelliferae), celery and parsley. Unwittingly, they are ingested by naive foragers and death occurs very rapidly. The third plant Anamirta derives from South-East Asia and contains a powerful convulsant, picrotoxin, which has been used from time immemorial to catch fish, and more recently to poison Birds of Paradise. All three poisons have been shown to block the γ-aminobutyric acid (GABA) system in the human brain that normally has a powerful inhibitory neuronal action. It has also been established that two groups of sedative drugs, barbiturates and benzodiazepines, exert their inhibitory action by stimulating the GABA system. These drugs are the treatments of choice for poisoning by the three vicious plants.

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The Sardinian poison and the Sardinian smile (risus sardonicus)

The Mediterranean island of Sardinia has a climate favourable to the cultivation of many sorts of cereals, such as corn, wheat and barley. As a result, it became known as ‘the granary of the Mediterranean’. Initially part of the Carthaginian Empire, the natives of the island rebelled during the first Punic war and ejected their North African oppressors.1 Seizing the opportunity, the Romans then took the short sea journey from Italy and occupied the island in 238 BC. When they arrived there, they were shocked to find that the Sardinians carried out a form of ritual murder in which they administered a poisonous plant (at the time ill defined) to criminals and elderly people. They then killed them by hitting them over the head or throwing them over steep cliffs. The Romans also noticed that the corpses all had a grimace on their faces (the sardonic smile). The Sardinians believed that as Heaven was a ‘happy place’ those souls would be welcomed if they had a smile on their faces.

Oenanthe crocata

For a long period, the nature of this poisonous plant and that of its poisonous chemical were undefined. When cut, its tuber exudes a yellow juice, hence Carl Linnaeus in 1753 gave the species the Greek name Oenanthe crocata (oenos – wine and crocata – yellow) (Figure 1). It is a member of the Apiaceae family (previously the Umbelliferae; the parasols).2,3 At first it was thought that the plant was confined to Sardinia but later it was recognised as being widely distributed in temperate North Europe. The plant is a perennial, closely related to cowbane, Cicuta virosa, but somewhat more poisonous. O. crocata prefers marshy and wet areas and grows to a height of three to five feet. The poisonous tubers can be exposed by flooding (Figure 2). Many deaths occur in children who are foraging (or digging) on the banks of water courses.4 The roots (tubers), which are the most poisonous part of the plant, resemble those of dahlias and the leaves those of parsnip and celery. The leaves have a fragrant smell and the roots taste sweet, two properties that encourage their consumption.

Figure 1 Oenanthe crocata; dead man’s fingers; hemlock water dropwort

Clinical features

Virtually all patients develop convulsions5 usually between 30 min and 1 hour after ingestion. They take the form of tonic/clonic muscle spasm accompanied by trismus.4–7 The contraction of the muscles may be so severe as to produce arching of the back (opisthotonus)5 akin to that seen in tetanus and strychnine poisoning. Contraction of the levator anguli oris muscles produces the classical sign, the sardonic smile (risus sardonicus) (Figure 3). The convulsions may also lead to biting the tongue, and this, together with the accompanying hypersalivation may produce blood-stained oral froth. Occasionally, nausea, vomiting (which may be profuse) and abdominal pain supervene first.5 If vomiting and convulsions occur simultaneously, aspiration pneumonia may result. Dilation of the pupils may also be observed together with tenderness of the muscles due to rhabdomyolysis, which has resulted in renal failure.5 Death usually occurs between 1–8 hours after ingestion and is due to progressive respiratory failure, secondary to refractory status epilepticus and ventricular fibrillation.5

Figure 2 The tubers of Oenanthe crocata (dead man’s fingers)


Airway care and seizure control are the two most important aspects of present-day management. Endotracheal intubation is vital but may present serious difficulties due to the spasm of the masseter muscles (trismus; lockjaw). Diazepam 10–20 mg intravenously in an adult (child 300–400 µg/kg) or intravenous lorazepam 4 mg in an adult (100 µg/kg in a child) may be effective if convulsions are only short lived.7 However, thiopental sodium is often needed to control repeated and sometimes refractory convulsions. One patient required it in a dose of 2–6 mg/kg/hour for 24 hours to control convulsions after diazepam and phenytoin had failed.6

Figure 3 Death mask of a victim of poisoning with Oenanthe crocata (the sardonic smile)

Cicuta virosa

C. virosa does occur in the UK but is sparse. Most of the severe cases of poisoning have occurred in the USA. This plant is known variously as water hemlock, beaver poison, wild carrot, wild parsley and false parsley (Figure 4).2 Water hemlock (Cicuta douglasii) is a member of the Apiaceae and can be confused with parsnip, celery, artichoke and also sweet anise. The flowers are typically of the umbel type – compact masses of heads.8 The plant has hollow stems and cavities in the root to keep afloat when flooded (Figure 5).

Figure 4 Cicuta virosa (cowbane)