Ricin is derived from the beans of the castor oil plant Ricinus communis. Many of the features seen in poisoning can be explained by ricin-induced endothelial cell damage, which leads to fluid and protein leakage and tissue oedema, causing so-called ‘vascular leak syndrome’. Immunization against ricin exposure using inactivated ricin toxoid or genetically engineered ricin A chain are realistic future therapeutic options. Abrin is a plant toxin obtained from the seeds of Abrus precatorius, which is closely related to ricin in terms of its structure and chemical properties.