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Ricin poisoning

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See also separate article Bioterrorism and Primary Care.

Ricin is derived from the beans of the castor plant (Ricinus communis). Castor oil beans are used to produce castor oil which is used in brake and hydraulic fluid, paints and varnishes. Castor oil is also traditionally used as a purgative. Ricin is normally inactivated during oil extraction and is not thought to remain in the oil.1

Ricin is usually lethal when injected or inhaled but most individuals who ingest it recover. Although it has been used as a means of assassinating individuals, this would make it difficult to use as an agent of mass warfare.2

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  • Ricin is a toxalbumin that can be extracted from the seeds of the plant. It can be produced in crystal or powder form and is soluble in liquids, therefore allowing potential for aerosol contamination.

  • Toxic effects produce inhibition of protein synthesis and cell death. This is thought to be related to inhibition of the RNA translation/transcription system.3

  • Ricin poisoning is so rare that even a single case, if confirmed, suggests deliberate release.

  • Potential routes of entry into the body are through inhalation, ingestion or injection.

    • It is a potential food or water contaminant.

    • It is stable in aerosol form and so allows ingestion by inhalation. This requires about a tenth of the dose needed by mouth.

    • Parenteral exposure is particularly lethal.

  • It is easier to produce than anthrax or botulinum toxin, although greater quantities may be needed for effect.4 It can potentially be made in a home laboratory.

  • If ricin were to be released by terrorists it would probably be within a closed environment.

  • There is no treatment or vaccine.


This will vary according to mode of exposure. After absorption by any route there may be delay before the onset of symptoms.

  • Gastrointestinal exposure

    • Onset of symptoms is usually within 12 hours.1

    • Irritation of the oropharynx and oesophagus as well as gastroenteritis.

    • Bloody diarrhoea, vomiting and abdominal pain.

    • Fluid loss may present as tachycardia or shock.

    • Liver and renal dysfunction and death can occur.

  • Aerosol/respiratory exposure

    • Onset of symptoms is usually within 8 hours.1

    • Pulmonary oedema, pneumonia, acute respiratory distress syndrome (ARDS) (particularly through aerosol exposure) and respiratory failure.

    • Irritation of the eyes and conjunctivitis, miosis, mydriasis and optic nerve damage.

  • Parenteral exposure

    • Nonspecific symptoms such as generalised weakness, myalgia, fever.

    • Vomiting, hypotension.

    • Local tissue damage at the injection site.

    • Multiorgan failure and death.

  • Other possible features

    • Seizures and CNS depression.

    • Rhabdomyolysis.

The features of ricin poisoning can be so nonspecific that a high index of suspicion is required to make the diagnosis.

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Initial management

  • If ricin poisoning is suspected, follow the Health Protection Agency's Deliberate Release - Emergency Clinical Situations algorithm.

  • In the case of multiple exposure to ricin, the triage sieve should be employed as described in major disaster plans. The Health Protection Agency (HPA) has produced a Chemical Action Card as an aide-mémoire to public health personnel.

  • Personnel treating potentially contaminated individuals need to have full personal protective equipment and respiratory protection as necessary.

  • Assess the need for decontamination and organise if necessary:

    • Affected individuals should be removed from the source of exposure. All of their clothing and personal effects should be removed. Skin decontamination should be carried out using a rinse-wipe-rinse regime with dilute detergent. A suitable form is 10 ml of washing-up liquid to a 10 litre bucket of water.

    • Contaminated clothing should be placed in clear, labelled, sealed bags to prevent further contamination.

    • After decontamination, re-dress in clean clothing such as paper suits.

    • If eyes are exposed, remove contact lenses and irrigate thoroughly with running water or saline for 15 minutes.

  • Environmental sample testing for ricin can be carried out.

  • Environmental decontamination also needs to take place as required.

Criteria for admission

  • Anyone who is thought to have ingested ricin should be admitted for observation but, if asymptomatic, may be discharged after 8 hours.

  • Anyone who is thought to have been exposed to the toxin by aerosol should be admitted for observation, even if asymptomatic but may be discharged if still asymptomatic after 24 hours.

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  • Ricin poisoning can cause multiorgan failure. Investigations may include:

    • Blood testing: full blood count, liver and renal function and clotting profile.

    • Haematuria and proteinuria may be evident.

    • Direct tissue analysis: techniques are currently being developed to allow detection of ricin in biological fluids.

    • CXR: may show an ARDS picture or pulmonary infiltrates.

    • X-ray can be helpful in parenteral exposure to look for any foreign body at the site of entry.

Differential diagnosis

  • Exposure to other agents such as anthrax, pneumonic plague and phosgene.

  • Food poisoning.

  • Respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD).


  • This is supportive.

  • Assess Airway, Breathing and Circulation.

  • Toxbase and the National Poisons Information Service (NPIS) may provide helpful advice (see link below).

  • Gastrointestinal exposure: perform gastric decontamination using activated charcoal. Fluid support and H2-antagonists are helpful.

  • Percutaneous exposure: try to excise the injection site as quickly as possible.

  • Aerosol exposure: this is supportive and may require ventilation.

  • Dermal exposure: contaminated clothing and jewellery should be removed as detailed above. The skin should be washed with soap and water. It is unlikely that dermal exposure can achieve toxicity but patients may be monitored for 12 hours for the development of symptoms.

  • If there are allergic reactions they should be treated in the usual way.


  • If death occurs it is usually within 36-72 hours of exposure. If the victim survives 5 days, death is unlikely.

  • Development work on human vaccines is currently underway.5

Historical note

  • In 1978 ricin was thought to have been used to assassinate a Bulgarian journalist called Georgi Markov. He was a critic of the Bulgarian government and was stabbed with the point of an umbrella while waiting at a bus stop near Waterloo Station in London. A perforated metallic pellet that was thought to have contained ricin toxin was found embedded in his leg.

  • In 2003, material that tested positive for the presence of ricin poison was recovered from premises in London and arrests were made.

  • Also in 2003, a package containing ricin and a note threatening to poison water supplies was discovered in a South Carolina postal facility in the USA. Emergency procedures were instigated, including environmental sampling and health assessment of personnel but no public health threat resulted.6 Ricin has also been found at a White House mail facility and a US senator's office.1

Further reading and references

  • Gosden C, Gardener D; Weapons of mass destruction--threats and responses. BMJ. 2005 Aug 13;331(7513):397-400.
  1. Audi J, Belson M, Patel M, et al; Ricin poisoning: a comprehensive review. JAMA. 2005 Nov 9;294(18):2342-51.
  2. Schep LJ, Temple WA, Butt GA, et al; Ricin as a weapon of mass terror--separating fact from fiction. Environ Int. 2009 Nov;35(8):1267-71. Epub 2009 Sep 19.
  3. Leshin J, Danielsen M, Credle JJ, et al; Characterization of ricin toxin family members from Ricinus communis. Toxicon. 2010 Feb-Mar;55(2-3):658-61. Epub 2009 Sep 23.
  4. Doan LG; Ricin: mechanism of toxicity, clinical manifestations, and vaccine development. A review. J Toxicol Clin Toxicol. 2004;42(2):201-8.
  5. Griffiths GD, Phillips GJ, Holley J; Inhalation toxicology of ricin preparations: animal models, prophylactic and therapeutic approaches to protection. Inhal Toxicol. 2007 Aug;19(10):873-87.
  6. Schier JG, Patel MM, Belson MG, et al; Public health investigation after the discovery of ricin in a South Carolina postal facility. Am J Public Health. 2007 Apr;97 Suppl 1:S152-7. Epub 2007 Apr 5.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • 20 Apr 2011 | Latest version

    Last updated by

    Dr Laurence Knott

    Peer reviewed by

    Import User
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