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Herbs - Roots - Vegetables
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Seed of Ricinus communis L.
(Castor seed / Castor bean)

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Although commonly referred to as a "bean," castor is not a legume. The plant has also been called the "castor oil plant." Castor oil, one of the oldest commercial products, was used in lamps by the Egyptians more than 4,000 years ago, and seeds have been found in their ancient tombs.

Castor is considered by most authorities to be native to tropical Africa, and may have originated in Abyssinia. While the castor-oil plant is a common summer bedding foilage throughout the USA, the production of oil from its seeds is at present [1961] confined to tropical regions. It can, however, be grown for oil in southern California, Texas, and in southern Florida.

The castor-oil plant is not native to Istria and is rarely seen to be grown there. However, castor-oil's medicinal properties have been known and were used among the Istrian people. Gabriele D'Annunzio is credited for originating the practice of forcibly dosing opponents with large amounts of castor oil to humiliate, disable or kill them during the brief period when he occupied Fiume (now Rijeka, Croatia) by force and declared himself dictator. This practice became a common tool of Fascist dictator Benito Mussolini and was used in Istria and undoubtedly elsewhere during the period of Italian rule between the two World Wars.

The shiny seeds of castor plants are a little larger than pinto beans and have very beautiful and intricate designs. At one end is a small, spongy structure called the caruncle, which aids in the absorption of water when the seeds are planted. Like human faces, finger prints or the spots on a leopard, no two seeds have exactly the same pattern. They are unquestionably among the most deadly seeds on earth, and it is their irresistible appearance that makes them so dangerous.

The many "faces" of castor seeds. Like the faces and fingerprints of people, the beautiful designs on castor seeds exhibit infinite genetic variation. The small structure on the end of each seed is a caruncle. The seeds superficially resemble the bodies of ticks, particularly ticks engorged with blood.

Castor oil

Castor beans are pressed to extract castor oil which is used for medicinal and other commercial purposes. Ricin does not partition into the oil because it is water-soluble, therefore, castor oil does not contain ricin, provided that no cross-contamination occurred during its production.

Castor bean poisoning

The seeds from the castor bean plant, Ricinus communis, are poisonous to people, animals and insects. One of the main toxic proteins is "ricin", named by Stillmark in 1888 when he tested the beansí extract on red blood cells and saw them agglutinate. Now we know that the agglutination was due to another toxin that was also present, called RCA (Ricinus communis agglutinin). Ricin is a potent cytotoxin but a weak hemagglutinin, whereas RCA is a weak cytotoxin and a powerful hemagglutinin.

Poisoning by ingestion of the castor bean is due to ricin, not RCA, because RCA does not penetrate the intestinal wall, and does not affect red blood cells unless given intravenously. If RCA is injected into the blood, it will cause the red blood cells to agglutinate and burst by hemolysis. Perhaps just one milligram of ricin can kill an adult.

The symptoms of human poisoning begin within a few hours of ingestion and these are:

  • abdominal pain
  • vomiting
  • diarrhea, sometimes bloody. 

Within several days there is:

  • severe dehydration,
  • a decrease in urine,
  • and a decrease in blood pressure. 

If death has not occurred in 3-5 days, the victim usually recovers.

Danger to children

It is advisable to keep children away from the castor bean plant or necklaces made with its seeds. In fact donít even have them in or around a house with small children. If they ingest the leaves or swallow the seeds, they may get poisoned. The highly toxic seeds beaded into necklaces, cause skin irritation at the contact point.

If the seed is swallowed without chewing, and there is no damage to the seed coat, it will most likely pass harmlessly through the digestive tract. However, if it is chewed or broken and then swallowed, the ricin toxin will be absorbed by the intestines.

It is said that just one seed can kill a child. Children are more sensitive than adults to fluid loss due to vomiting and diarrhea, and can quickly become severely dehydrated and die.

Castor bean plants in a garden should not be allowed to flower and seed. A good practice is to "nip it in the bud".


In 1978, ricin was used to assassinate Georgi Markov in 1978, a Bulgarian journalist who spoke out against the Bulgarian government. He was stabbed with the point of an umbrella while waiting at a bus stop near Waterloo Station in London. They found a perforated metallic pellet embedded in his leg that had presumably contained the ricin toxin.

Danger to animals

Aphids, drawn above on a leaf of the castor bean plant, are susceptible to poisoning from ingesting the phloem. The sap-suckers died within 24 hours of feeding.

The European corn borer and the Southern corn rootworm larvae were killed when exposed to feed painted with 2% ricin. Studies like these are undertaken to develop "natural" pesticides.

Castor beans are used as an ingredient in some animal feeds after the oil has been extracted or inactivated by heating for 20 minutes at 140° C. Attempts to use castor beans in feed for livestock involve different methods of inactivating ricin while maintaining nutritional value. Some studies have shown that even afte such heat treatment, toxicity remains. For example, it was lethal to mallard ducks given the feed. "The toxicity of the meal could be due to either a heat stable or growth inhibiting factor or due to minute residues of ricin"(Okoye et al.)

A study with sheep showed that autoclaved castor-bean-meal can be incorporated to 10% of sheep rations without any ill effect.

Poisoning of livestock usually occurs by accidental incorporation of castor beans in their feed. Horses are particularly vulnerable.

For more detailed information about effects of Ricin on livestock, see... "Poisonous Plants Page, Ricinus Communis,

Medicinal Usage

The oil from the seed is a very well-known laxative that has been widely used for over 2,000 years. It is considered to be fast, safe and gentle, prompting a bowel movement in 3 - 5 hours, and is recommended for both the very young and the aged. It is so effective that it is regularly used to clear the digestive tract in cases of poisoning. It should not be used in cases of chronic constipation, where it might deal with the symptons but does not treat the cause. The flavour is somewhat unpleasant, however, and it can cause nausea in some people. The oil has a remarkable anti-dandruff effect. The oil is well-tolerated by the skin and so is sometimes used as a vehicle for medicinal and cosmetic preparations. Castor oil congeals to a gel-mass when the alcoholic solution is distilled in the presence of sodium salts of higher fatty acids. This gel is useful in the treatment of dermatosis and is a good protective in cases of occupational eczemas and dermatitis. 

The seed is anthelmintic, cathartic, emollient, laxative, purgative. It is rubbed on the temple to treat headache and is also powdered and applied to abscesses and various skin infections. The seed is used in Tibetan medicine, where it is considered to have an acrid, bitter and sweet taste with a heating potency. It is used in the treatment of indigestion and as a purgative. A decoction of the leaves and roots is antitussive, discutient and expectorant. 

The leaves are used as a poultice to relieve headaches and treat boils.


  • Cathartic, demulcent, analgesic, nervine, purgative.
  • root bark-purgative.

The oil pressed out of the seeds is one of the most commonly used purgatives. Castor oil is described in Ayurveda as the "king of the purgatives" and "king of vayu disorders." Castor oil acids are anti- absorbative and hydragogic.

Ricini semen exhibits proven anti-viral effects.


  • abdominal disorders
  • colic
  • enlarged liver and spleen
  • fever
  • headache
  • lumbago
  • nervous diseases
  • pain relief (joints)
  • promote menstrual discharge
  • promote milk production
  • rheumatism
  • sciatica

Externally, the seeds and leaves of this herb are used in powder form as a poultice for inflammatory skin disorders, boils, carbuncles, abscesses, inflammation of the middle ear and migraine.

Internally, the drug is used as a purgative in the treatment of acute constipation, intestinal inflammation, worms and as a form of birth control.

C.K.N. Nair and N. Mohanan, authors of "Medicinal Plants of India," describe the application of this herb in Ayurveda as follows:

"The oil, roots, seeds and leaves. Many medicinal uses. Root-bark, leaves and oil are purgatives. Oil used in rheumatism and many other medicinal preparations. Leaves are galactagogue. Decoction of root is a remedy in phlegm, swellings, stomach-aches, dropsy, fever, hernia, asthma, leprosy, rheumatic joints and all pains in the wrist, head and bladder. It cures rheumatism and stone in the bladder. Seeds ground and eaten cure rheumatism and liver complaints."


  • Oil doses: children - 1 tsp.; adults - 2 tsp. - 3 tbs. in tea or boiled milk. Decoction, infusion, poultice, leaf, paste.
  • For internal use: Take at least 10.0 gm for acute constipation or as a purgative against worms. 
  • For external use: Use a paste made from ground seeds. Apply this paste to the affected skin areas twice daily. A course of treatment may take up to 15 days.

Warnings and precautions:

The entire plant, including the seeds, contains an irritant substance that poisons the blood, but commercially prepared castor oil contains none of the ricin toxin. The oil is safe because the poison remains in the seed. Castor beans are severely poisonous to people, animals and insects. The coats of castor beans contain high concentrations of deadly ricin, a toxic protein for which there is no known antidote. Just one milligram of ricin (one of the main toxic proteins in the plant) can kill an adult. The ricinus lectins act by inhibiting protein synthesis by destroying the ribosomes. The seed is only toxic as the outer shell is broken or chewed open. Thus, you should not grow castor beans where children play; the seeds are just too pretty and too deadly. Children have died from eating castor bean seeds. 

Other precautions:

  • Allergy-related skin rashes have been observed in some very few cases. 
  • Do not use castor oil if you are suffering from kidney, bladder, bile duct, intestine infections or jaundice. Do not use if you are pregnant or nursing.
  • No health hazards or side effects are known if this herb is administered properly with designated therapeutic dosages of castor oil. 
  • Long-term use of this herb can lead to losses of electrolytes, in particular K+-ions. This can result in hyperaldosteronism, inhibition of intestinal motility and enhancement of the effect of cardioactive steroids.
  • Do not administer this drug to children under 12 years of age.
  • Overdoses of this herb can lead to gastric irritation, accompanied by queasiness, vomiting, colic and severe diarrhea. Twelve castor beans are believed to be fatal for an adult. Symptoms include severe gastroenteritis, with bloody vomiting and bloody diarrhea, kidney inflammation, loss of fluid and electrolytes and ultimately circulatory collapse. Death is usually the result of hypovolemic shock.

Commercial Usage

Parts used: oil, leaves, roots, seeds, fruit

Ricinus communis has had economic use in many parts of the world for its medicinal properties, despite potential toxic effects. Castor oil has been used for many years as a purgative, laxative, and general cure all. In warmer regions of the world, the plant is grown for the seeds from which castor oil is extracted (Muensher 1939). 

The plant has been used for a variety of purposes for quite some time. Egyptians burned caster oil in their lamps and castor beans have been found in ancient Egyptian tombs dating back to 4,000 BC. The plant is a native of India and Africa and the fixed oil is obtained by expression from the seeds. It has been used therapeutically and medicinally in ancient India, China, Persia, Egypt, Africa, Greece, Rome, and in 17th century Europe. 

In the United States, castor oil has been used by the military in aircraft lubricants, hydraulic fluids, and in the manufacture of explosives. It is now of importance in a wide variety of technical applications due to its unique content of ricinoleic acid. The oil is used, for instance, in the manufacture of some lubricants, plastics, surfactants, paints, and dyes, and in the preparation of imitation leather. Textile scientists have used sulphonated (or sulfated) castor oil in the dyeing and finishing of fabrics and leather. It has also been used in the synthesis of soaps, linoleum, printer's ink, nylon, varnishes, enamels, paints, and electrical insulations. It is also found in many commercial skin care products. When it is used in the manufacture of soap it forms a clean, light-colored soap with a stable lather, which dries and hardens well. It is used for hair conditioners treating conditions such as dry or brittle, damaged hair or hair loss (as a very thick oil with a slight but prominent odor and slightly sticky texture). It is also often used as an emollient and skin softener, and, being free from smell, and has been recommended for medicinal use as a treatment of gastrointestinal problems, lacerations and other skin disorders such as psoriasis. The most infamous application of castor oil may have been as a purgative popular for the treatment or prevention of many ailments in the first half of the twentieth century.

Castorbean meal is included as a protein source in feed for swine. Castorbean pomace, or meal, the residue left after the oil has been extracted from the seeds, has been included in mixed fertilizer. This product contains the ricin and ricinine from the seeds. Certain varieties of castorbean plants are grown as ornamentals. 

India is currently the largest producer of castor oil in the world (Gandhi et al. 1994), but it has also been grown commerically in California and the Southern U.S. (Hardin 1974). Other uses of the extracts of Ricinus communis include as an additive in paints and varnishes, as an additive in high-preformance motor oil, and as the raw material from which sebacic acid is extracted. Sebacic acid is a primary component used in production of nylon and other synthetic fibers. Another commercial application for the bi-products and remnants from castor oil production that is being explored is as an additive in animal feeds. A method involving detoxification of the highly toxic castor seed meal by addition of sal seed meal has been devised by a group of India researchers (Gandhi et al. 1994). This use of the Castor Bean is surprising, since ricin can kill laboratory animals at concentrations as low as 10 micrograms/kg. For this reason, castor seed meal is not normally desirable as an additive in animal feeds. Methods to detoxify the meal, such as heating or treating with alcohol and aqueous HCl are undesirable since they also destroy nutritive protiens thus making the meal low quality for animal feeds. By mixing the meal with sal seed meal, which contains a high concentration of tannins, the toxic effect of the castor bean meal was effectively neutralized without destroying the nutritive quality of the meal. According to Gandhi et al. (1994), "[n]aturally-occurring food tannins react with proteins, including enzymes, to form tannin protein complexes that lead to inactivation of digestive enzymes. In this way tannins interfere with protein digestibility and absorption."

  • Text - Norman Taylor, Taylor's Encyclopedia of Gardening, 4th Ed., Houghton Mifflin Company, Boston (Cambridge, 1961), p. 198, 737.
  • Photographs - Ricinus communis -
  • Text and photographs - Castorbean -
  • Photograph -
  • Botanical online -
  • Floridata - Ricinus communis -
  • Medicinal uses -
  • Photographs -

See also:

  • Terror, Muder and Medicine -
  • Purdue University, Castor: Return of an old crop -
  • Purdue University,
  • Rare books from the MBG Library, Kohler's Medizinal Pflanzen (1761 drawings) -

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Created: Monday, February 09, 2004; Last Updated: Wednesday, October 05, 2016
Copyright © 1998, USA