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Ricinus communis, castor oil plant


Usually described as absolutely deadly in the tiniest of amounts; 50,000 tonnes a year being produced; usually said to be reasonably easy to extract from the plant; so why has ricin killed hardly anyone since 1978?

'Poisonous Plants 1-2-1' video

This short video summarising the story of the castor oil plant is just one of a series.



Meaning of the Name

A circular definition is usually given i.e. ‘ricinus’ means ‘tick’ because the skin of the castor beans looks like a tick. But there is a tick called iloxedes ricinus named because its skin looks like a castor bean. Possibly from the Latin ‘ri’, ‘thing’ and ‘cinus’, ‘destruction’, ‘the dead’, ‘ruin’, thus, the thing which brings death.

Common Names and Synonyms

castor bean plant, true castor oil plant, hand of Christ (palma Christi). Fatsia japonica, the false castor oil plant, is often sold as 'castor oil plant' though the two have nothing in common apart from their appearance.

How Poisonous, How Harmful?

Ricinus communis, castor oil plant

Ricinus communis, castor oil plant

As quite a strong laxative, castor oil can be the cause of harm, especially if it is ingested accidentally as a result of spray from its use as a lubricant, but it is the substance left in the residue after the beans have been crushed to produce the oil which makes Ricinus communis such a notorious plant. Because those residues contain ricin.

Ricin, a simple protein, is believed to be one of the most toxic naturally occurring substances and is often mentioned as a potential terrorist weapon for causing mass murder in spite of all evidence to the contrary. The plant also contains Ricinus Communis Agglutin (RCA) which causes increased coagulation.

If ingested, it causes vomiting which in many cases expels the poison and prevents death. If injected or inhaled it causes stomach pain, dehydration and destroys the main internal organs. With no antidote, treatment relies on symptomatic support and the use of heart lung machines, kidney dialysis, etc. After 3-5 days symptoms diminish though death may take about the same time to occur.

But, though ricin is extremely poisonous it actually does little harm. Around one million tons of castor beans are processed each year for castor oil production leaving the waste pulp with up to 50,000 tons of ricin in it. And, yet, finding instances of ricin poisoning is not an easy task.

So how is it that this exceptionally toxic substance fails to achieve its harmful potential?

Ricinus communis, castor oil plant

Ricinus communis, castor oil plant

There are three main ways to administer a poison; ingestion, inhalation or injection. Val McDermid in her book ‘Beneath the Bleeding’ has found a fourth, see the box below, but that is unlikely to become common.

As above, ricin is extremely emetic, if ingested. A 1985 report from the Emory University School of Medicine and the Georgia Poison Control Center examined 751 cases of accidental ricin ingestion during the previous 85 years. They found only 15 deaths (1.9% mortality) in these cases, an indication of the problems of causing death by ingestion of ricin. The researchers went on to look at those deaths in more detail and concluded that, with modern symptomatic support methods, a number of them could have been avoided. They estimate that, today, fatality from ingestion is likely to be around 0.4%. Feeding ricin to the masses is, thus, not likely to be an efficient way to cause multiple deaths.

Experiments have shown that inhalation of even tiny amounts of ricin is fatal and this leads to many stories of plans to spray ricin into the general population, especially on underground train networks. What these scare stories ignore is that, in the experiments, the animals used were fitted with face masks and forced to inhale the ricin. Ricin is an extremely large molecule and, normally, forms large particles which fall to the ground quickly, especially in the presence of any draught. Its use as an aerosol spray would be unlikely to produce any deaths.

A paper published in 'Environment International' in November 2009 by Schep at al, contains an extensive review of the literature on ricin and points out that to have a serious effect by inhalation ricin powder would need to be milled to a very small particle size. The authors say this may be possible for a rogue government to do but is not something small terrorist groups would be able to achieve.

Ricinus communis, castor oil plant, source of ricin

Ripening fruits of Ricinus communis

The authors do say that there is a very small possible that terrorists could produce enough ricin to poison a small water supply and cause non-fatal symptoms of poisoning. Such an event could cause substantial panic given the media's ill-informed paranoia about ricin.

The Hampstead and Highgate Express published the obituary of Professor John Henry, described as Britain's best known toxicologist. Prof Henry was an expert witness in the Leah Betts ecstasy death case and identified the poison, dioxin, used on Victor Yushchenko, just from a photograph. According to the newspaper he also ‘diffused tabloid hysteria about the planned ricin attack on the London underground by pointing out that London commuters could in fact swim in ricin without suffering any harm - it was only fatal if injected into the bloodstream.’

So, for ricin to be as actually harmful as it is theoretically, it must get into the bloodstream and, unless terrorists find a way to get people to line up and receive an injection, the sad fact is that there are plenty of better weapons available to the renegade government or terrorist wishing to mount an attack.

In an elliptical sort of way, ricin can be said to have contributed to tens of thousands of deaths. In January 2003, as the Bush government was trying to build its case to invade Iraq, British police raided premises in North London and, then and later, arrested  nine men. They were said to be a terrorist cell and, it was alleged, the premises raided were being used as a 'factory' to produce biological weapons. Samples were removed which were thought to be ricin. In the event, no ricin was found and eight of the nine men charged were freed after four were found not guilty and the charges against another four were dropped. The ninth, Kamel Bourgass, was convicted of 'conspiracy to cause a public nuisance by the use of poisons' having, earlier, been convicted of the murder of a police officer attempting to arrest him.

The importance of this event, however, is that on 5th February, 2003 US Secretary of State, Colin Powell, gave a speech to the UN Security Council arguing for a resolution in support of war on Iraq. In this speech, he referred to intelligence reports pointing to the intention of Iraqi backed terrorists to launch 'poison and explosive' attacks in Europe and said that the unearthing of a terrorist cell in Britain in January proved that this intelligence was valid.

Though Powell did not, specifically, identify the so-called 'ricin plot', it didn't take long for the press to make the connection. (It is a common ploy to give journalists enough information so that they find data for themselves which removes their scepticism about information being fed to them.) This apparent confirmation of the veracity of US intelligence reports is believed to have been key to the decision to invade Iraq. It is widely believed that UK Prime Minister, Tony Blair, himself brought the 'ricin plot' to the attention of George Bush resulting in its inclusion in Colin Powell's evidence.

To this day, some writers continue to talk about ricin as a potential bioterrorism weapon insisting that Iraq was producing ricin but completely ignoring the evidence that this production was small-scale, terminated in the mid-1990s and was for use in assassinations; its use as a weapon of mass destruction having been found to be impractical. As recently as January 2013, the press reports on a case concerning whether one of the eight men arrested in 2003 could be deported contained references to the 'ricin plot' in spite of there being no such thing.

Watch a Video about Ricin

Click in the window above to watch a ten minute video about Ricinus communis and ricin.


The best known incident of ricin poisoning was the 'umbrella murder' of Georgi Markov in London in 1978. Markov was waiting for a bus when he felt a sting to the back of his thigh. He looked round to see a man picking up an umbrella. The man apologised in accented English and got into a waiting taxi. Following his, death three days later Markov was found to have a small pellet imbedded in his thigh with holes drilled in it. Though no metabolites of ricin were detected, experts concluded that the most likely cause of the poisoning was that a small amount of ricin had been present in the pellet, held in place by a covering of a substance that would melt at body temperature. This 'best guess' is reinforced by the discovery of antibodies in Vladimir Kostov (see next paragraph). The British press decided that the umbrella had been used as the means of delivering the pellet and the story of the 'umbrella murder' entered folklore.

Ricinus communis, castor oil plant, source of ricin

Flowering Ricinus communis, castor oil plant

What is less well known is that a couple of week’s before Markov’s death, Vladimir Kostov, a fellow Bulgarian dissident living in Paris was taken ill but recovered after 12 days. When the possible cause of Markov’s death was becoming clear Kostov was x-rayed and found to have a tiny pellet still imbedded in his flesh. The significant difference seems to be that Kostov was 'shot' in the back through several layers of clothing. It would appear that this slowed the pellet enough for it not to penetrate far enough for the poison to get fully into his bloodstream. It could also be that the protective coating had already failed so that the ricin leaked away or that it failed to fully dissolve. Kostov was, however, found to have ricin antibodies in his bloodstream so he had been exposed to the poison. There was never any mention of an umbrella in the Kostov case.

The circumstances of Kostov's poisoning help to construct the most likely scenario for the attack on Markov. Dropping an umbrella would have served three purposes for the murderer. First, he would have been able to approach more closely to Markov than would have seemed normal if he were not retrieving a dropped item. Second, his lower body position would give him access to Markov's thigh where only one layer of material needed to be penetrated. And third, like any magician, the murderer was creating a diversion so that anybody watching would be focussing on the hand picking up the umbrella and not looking at the other hand, thought to have contained a small modified air pistol using compressed air to fire the pellet.

The umbrella story was given new credence, apparently, in the 1990s when a former KGB officer said that he had dealt with the request from the Bulgarian Secret Service for help in killing Markov and that Andropov, the then Soviet leader, had authorised technical assistance but not active involvement. The KGB officer said he knew where the KGB had designed and built the modified umbrella. This was only a small part of the officers stories about his time in the KGB. Those who have studied his writings say that many things do not stand up to scrutiny and some can be found in spy fiction. On the Markov case, the officer said Kostov had been attacked after Markov.

Like the ricin plot that wasn't, the press continues to refer to Markov's killing as the 'umbrella murder'. As mentioned above, there has never been any suggestion that an umbrella played any role in the Kostov attack. It would seem to be very odd for the KGB to develop a weapon for delivering a small pellet of ricin into Kostov's back and then develop another weapon to use on Markov. 

A more recent 'incident' turns out not to be an incident at all. In late 2010, CBS reported that the USA's Department for Homeland Security (DHS) had issued a warning about the possibility of terrorists contaminating the food in restaurants and hotels. This rapidly got re-reported by other media and soon became an actual plot. These days, articles about ricin talk about 'the plot to poison thousands reported by the DHS' and the like.

The DHS refuses to give a full explanation of what happened though it does say it has never issued a public warning about such a plot. As far as can be assessed, it seems that the DHS gave a routine briefing to security managers involved in the hospitality industry about what to look out for in the event of an attempt to cause poisoning via contamination of food served to the public. Word of this event reached the media who then created the 'plot'.

As a result, a journalist for a proper scientific publication writes about 'a recent bioterrorism attack plot targeting US hotels and restaurants at multiple locations'. (I won't perpetuate the myth by linking to the piece.)

Ricinus communis, castor oil plant

Ricinus communis, castor oil plant

The Centre for Non-proliferation Studies website has a detailed chronology of ricin, click here (opens a new window), but lists no cases, since 1978, where it has been used successfully to kill.

This interesting blog post dispels many of the myths about ricin as a weapon.

A letter to the British Medical Journal, in 1905, reports the case of a 28-year old man who ingested one castor bean and suffered immediate burning of the mouth and eyes followed by collapse. He was admitted to hospital with very shallow breathing and no measurable pulse. He had no diarrhoea and was, during his stay, treated to relieve constipation. He received emetics and stimulants and, by the next day, his pulse and respiration were normal. He remained in hospital under observation for a few days but was released fully recovered.

The symptoms described, the rapidity of their onset, the absence of abdominal symptoms and diarrhoea and the equally rapid recovery cast doubt over whether the poisoning agent was correctly identified leading to correspondence on both sides of the argument but no conclusive resolution.

The paper by Schep et al referred to above does give details of deaths due to the injection of ricin. In all but one of these the deaths were suicide. The only reported murder was part of a murder suicide reported, briefly, in 2004.

A very elderly man recounted his experience when a prisoner of the Japanese in Thailand during WWII. He and about 200 other men were out on a work party when they came across a large number of bushes all bearing fruit. They fell upon them and ate the fruit which was later identified as from the castor oil plant. All suffered severe diarrhoea and two died, though whether as a direct result of ricin or simply due to the effect of the diarrhoea can never be established.

Fruit of Ricinus communis, castor oil plant

Fruit of Ricinus communis,
castor oil plant

An August 2009 paper written by doctors in Belgium reported on the case of a 49 year-old man who committed suicide by injecting himself with ricin. He was admitted to hospital 24 hours after the injection and died nine hours later in spite of  symptomatic intensive care support. Death resulted from multi-organ failure following nausea, vomiting, diarrhoea, vertigo and muscular pain.

Incidents related to the overuse of castor oil are more light-hearted for the reader though not for the participants.

An Australian visitor to the Alnwick Garden Poison Garden talked about a man who suffered serious diarrhoea which cleared up quickly if he took time off work but returned when he returned to work. She was working at a poison information centre and was asked if she could suggest any possible causes. Acting on her advice it was discovered that the machine which the man used at work was faulty causing a fine mist of lubricating oil to be present in the air. The lubricant was castor oil. As soon as the machine was repaired the man’s diarrhoea cleared up for good.

Early aircraft, like the Sopwith Camel, used a rotary engine where castor oil was used as a lubricant. The oil would mix with the fuel/air combination in the cylinder but would only be partly burnt. The exhaust from these engines would, therefore, contain an amount of unburnt castor oil. As well as making the engines oil hungry and, therefore, increasing the need for maintenance, this unburnt oil was the cause of dirty streaks along the fuselage. It was said that this could cause visibility problems for the pilot and so cowlings were installed to direct the exhaust flow under the fuselage. There is no mention, other than anecdotally, of the other problem which could be expected by exposing pilots to castor oil-laden fumes.

Folklore and Facts

Val McDermid’s book ‘Beneath the Bleeding’ is the story of a serial poisoner who uses various plant extracts as his murder weapons. The case discussed in most detail involves ricin being applied to the body, during a sexual encounter, in a place where it might reasonably be expected to enter the bloodstream.

Let's just say that, had the victim survived the poisoning, they would have found sitting down uncomfortable.

In spite of the lack of any actual incidents and the near impossibility of using ricin to mount a terrorist attack, the plant is viewed with some suspicion. An American said that she had purchased 6ozs of castor beans online after being told that they would harm moles. A couple of days after the beans arrived she was visited by an FBI agent who knew a great deal about her and wanted to know what she was planning to do with the beans.

Another American said that she had buried castor beans all around the perimeter of her property because she had been told this would keep gophers out. Online sources talk about putting castor beans down gopher holes in the hope they will eat them or growing the plant around the perimeter as its roots are said to be toxic to gophers. An American Cable TV gardening programme, broadcast in November 2004, talked about a new product made by mixing castor oil with ground corncobs and soap and milling the mixture into granules. The granules release the castor oil smell when they get wet and this is said to repel gophers and moles without hurting them. It should be said that other sites say there is no evidence for efficacy of any of these methods of gopher control.

The status of ricin as a potential terrorist weapon is an example of the continuing development of plant folklore which many people think of as somehow being set in past times. Whether through ignorance or a desire to misdirect potential terrorists, the US authorities, in particular, continue to put ricin forward as something to be feared in ways which almost parallel old beliefs about the devil and Atropa belladonna, deadly nightshade.

It is, frequently, stated that ricin can be easily extracted from castor beans and that recipes are readily available on the Internet. The majority of these recipes can be traced back to a bulletin board favoured by school and college students (almost exclusively boys) in the 1990s. In fact, the recipe does no more that dry the castor bean mash left after the oil has been pressed. The level of knowledge of the author can be seen from his description of castor oil as a cough medicine and his statement that he doesn't know where to get castor beans.

Ricin is, also, not particularly stable and the crude extraction methods proposed would likely destroy a large proportion of the toxin.

Sources - Papyrus Ebers

The Ebers Papyrus, is named after the Egyptologist who first possessed it after its discovery in the mid 19th century. It has been dated to around 1500BC but, since it is clearly a collection of well-known remedies rather than a new work, it is taken to show that the Egyptians had a well developed system of medicine possibly as far back as the First Dynasty, 3400BC. It is unclear whether there was a single author or several people contributed to its production.

Perhaps its best known remedy is the use of opium to help a baby go to sleep.

The fascination with ricin as a weapon was, again, demonstrated in June 2009 when the UK's National Archive declassified a 1945 report entitled 'The Use of Chemical Darts from the Air'. This report looked at work to develop a system for dropping small poisoned darts directly onto enemy troops. According to press reports covering the release of the report, the poison to be used was 'probably anthrax or ricin'. The report actually says that for such a weapons system to be effective it must disable immediately and kill within fifteen minutes. An appendix says that a compound designated T.1123 which is a nerve agent has been selected after a number of unnamed substances were tested. A substance, designated only as 'X' is given as a possible alternative though its effects are not immediate. It is reported that 'X' causes vision impairment, paralysis and death within 12 hours.

It is quite clear that ricin does not meet the criteria specified and is neither compound T.1123 nor substance 'X' but, it appears, the media are so obsessed with ricin that they cannot bring themselves to report a chemical/biological weapons story without including ricin as the villain of the piece.

Ricinus communis Gozo

Hundreds of seedpods on a plant in Gozo

The ancient Egyptians were familiar with the ‘castor oil tree’ and made extensive use of castor oil and other parts of the plant in the remedies collected in the Ebers Papyrus. It appears in over 100 prescriptions. As might be expected it was drunk as a cure for constipation but it was also rubbed on the head to cure headaches or to promote growth of hair for a woman. In these instances it is used on its own but it also gets mixed with all manner of other items. With yeast and water, it would cure roundworm. With red lead it was capable of curing herpes on the face. The leaves, mixed with honey and ‘clay from a statue’ and applied as a poultice would treat a ‘flow of matter’ from both eyes.

Though I haven't read anything on the subject, I have noticed that the plant seems to have disappeared from local authority plantings. I hadn't seen Ricinus communis in a municipal flowerbed or tub for about three years when, in 2017, I holidayed on the Maltese island of Gozo and saw a massive plant growing wild adjacent to a seating area at the roadside in the middle of a village. One can only wonder what the British press would make of seeing the hundreds of seed pods on this single plant well within reach of anyone passing.

Earlier Blog Entries;

You can read more about Ricinus communis and ricin in these blog entries (most recent first);

Podcast from the Royal Society of Chemistry has disappointing errors
Ricinoleic acid is not ricin and is not a poison
Mail Online publishes truly dreadful story about ricin
Research suggest drinking milk might be enough to stop ricin poisoning
The plants put out by the council make mine look very small
Herbal remedy containing ricin causes death
Official US report says ricin is not a WMD
Press still refers to ricin plot in 2003 to support biased reporting
Video of Oklahoma House of Representatives session on castor bean reveals amazing stupidity
Oklahoma intends to outlaw the commercial growing of castor bean
At last, two scientific papers giving facts about ricin's lack of success in killing
The press release used by the Daily Mail is the source of the lies
Daily Mail lies about ricin misrepresents the purpose of new research
A Remembrance Day look at plants associated with war and soldiers
Another 'ricin plot' this time featuring four silly old men from Georgia
Harmless white powder causes evacuation of 700 employees at the Student Loans Company
Scientific principles are being abused to try and make the case for ricin as a weapon
'The Poisoner's Handbook' today and in 1988
Claims about 'ricin bombs' are being used to justify the US killing its own citizens.
The problem caused by 'sciencey' names saying nonscience things.
33 years since Georgi Markov's murder. The 'Umbrella Murder' that wasn't.
Is the US government trying to keep the elephants away?
Satirical take on the 'ricin bomb' nonsense
The New York Times publishes scare story about ricin but forgets to say it is a book puff
More examples of the media's obsession with ricin
Bogus claims about ricin poisoning plot

Return to recent entries.


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Introduction to the A to Z section
Abrus precatorius, rosary pea
Aconitum lycoctonum, wolfsbane
Aconitum napellus, monkshood
Actaea racemosa, black cohosh
Actaea spicata, baneberry
Aesculus hippocastanum, horse chestnut
Amanita muscaria, fly agaric
Aquilegia atrata, columbine
Aristolochia clematitis, birthwort
Artemisia absinthium, wormwood
Arum italicum, Italian cuckoopint
Arum maculatum, cuckoopint
Aspergillus fumigatus
Atropa belladonna, deadly nightshade
Brugmansia suaveolens, angel's trumpet
Bryonia dioica, bryony
Buxus sempervirens, common box
Camellia sinensis, tea
Cannabis sativa, marijuana
Catha edulis, khat
Chelidonium majus, greater celandine
Cimicifuga racemosa, black cohosh
Claviceps purpurea, ergot
Clematis vitalba, old man's beard
Colchicum autumnale, naked ladies
Conium maculatum, poison hemlock
Convallaria majalis, lily of the valley
Cynoglossum officinale, hound’s tongue
Daphne mezereon, spurge olive
Datura stramonium, thorn apple, jimsonweed
Datura suaveolens, angel's trumpet
Delphinium, larkspur
Digitalis spp., foxglove
Dracunculus vulgaris, dragon arum
Echium vulgare, viper’s bugloss
Eranthis hyemalis, winter aconite
Erythroxylum coca, cocaine
Euonymus europaeus, spindle tree
Euphorbia x martinii, red spurge
Euphorbia pulcherrima, poinsettia
Fritillaria spp., fritillary
Galanthus nivalis, snowdrop
Hedera helix, common ivy
Helleborus spp., hellebore
Heracleum mantegazzianum, giant hogweed
Hyacinthoides non-scripta, bluebell
Hyoscyamus niger, black henbane
Ilex aquifolium, holly
Jacobaea vulgaris, ragwort
Juniperus communis, common juniper
Laburnum anagyroides, laburnum
Lactuca serriola, prickly lettuce
Leucojum aestivum, snowflake
Lithospermum officinale, gromwell
Lolium temulentum, darnel
Malus 'John Downie', crab apple
Mandragora officinarum, mandrake
Mercurialis perennis, dog’s mercury
Narcissus, daffodil
Nepeta faassenii, catmint
Nerium oleander, oleander
Nicotiana sylvestris, tobacco
Oenanthe crocata, hemlock water dropwort
Papaver somniferum, opium poppy
Pastinaca sativa, parsnip
Polygonatum odoratum, angular Solomon's seal
Prunus laurocerasus, cherry laurel
Pulsatilla vulgaris, pasque flower
Ranunculus acris, meadow buttercup
Rheum x hybridum, rhubarb
Rhododendron spp.
Rhus radicans, poison ivy
Ricinus communis, castor oil plant
Rosmarinus officinalis, rosemary
Rumex obtusifolius, broad-leaved dock
Ruta graveolens, rue
Salix alba, white willow
Salvia divinorum, sage
Scutellaria laterifolia, Virginian skullcap
Senecio jacobaea, ragwort
Solanum dulcamara, woody nightshade
Solanum melongena, aubergine
Strychnos nux-vomica, poison nut
Symphoricarpos albus, snowberry
Symphytum spp., comfrey
Taxus baccata, yew
Toxicodendron radicans, poison ivy
Thevetia peruviana, yellow oleander
Urtica dioica, stinging nettle
Veratrum album, white hellebore
Verbascum olympicum, Greek mullein
Vinca major, greater periwinkle
Viscum album, mistletoe
Vitex agnus-castus, chaste tree