Ricin is a protein toxin that is readily produced from castor beans (Ricinus communis), which are available throughout the world. It acts as a cellular poison by inhibiting protein synthesis. Naturally-occurring cases of ricin involve ingestion of castor beans, and are marked by severe gastrointestinal symptoms, vascular collapse, and death.

Ricin has been used as a biological weapon for assassinations in the past. It is toxic by numerous exposure routes; however, its use by bioterrorists might involve poisoning of water or foodstuffs, inoculation via ricin-laced projectiles, or aerosolization of liquid ricin or lyophilized powder. Waste from the commercial production of castor oil contains 5% ricin, making it easy for such a substance to fall into the hands of bioterrorists.


When inhaled as a small particle aerosol, ricin generally produces symptoms within 8 hours. Fever, cough, difficulty breathing, nausea, and chest tightness are followed by profuse sweating, skin turning blue, low blood pressure, and finally respiratory failure and circulatory collapse. Time to death would likely be 36-72 hours, depending on the dose received.


The diagnosis of ricin is largely based on symptoms and should be suspected in a setting of mass casualties with a similar and appropriate clinical picture. Failure to respond to antibiotics helps to differentiate ricin exposure from lung infections produced by bacterial agents. A blood antibody test exists but is not readily available. No specific treatment exists, and care is thus supportive treatment of symptoms. No specific vaccine or antitoxin exists. A protective mask would offer protection from aerosol exposure.