Little mention has been made of castor bean poisoning in the American medical literature. This bean is the brown mottled seed of the castor plant, Ricinus communis, from which castor oil is extracted. It is about one and one-half times the size of a lima bean. Although of tropical origin, the castor plant has frequently been transplanted to the temperate zones because of its ornamental foliage.
The castor bean, because of its poisonous constituent ricin, is a potent toxic agent. In human beings severe symptoms have resulted from inhaling the dust of the bean. This has been known to cause severe anaphylactoid reactions of the respiratory system in hypersensitive persons. More commonly, however, intoxication results from the inadvertent ingestion of the bean. Ricin is an extremely poisonous protein (phytalbumin) found in the seeds along with the oil. When commercially extracted, however, castor oil contains little or no ricin.