The other toxic protein in the castor bean, RCA (Ricinus communis agglutinin), agglutinates red blood cells. In other words, injection of RCA into the bloodstream essentially causes a person's blood to coagulate. Ingestion of a castor bean or its products will release ricin, but the RCA cannot cross the intestinal wall.
Castor oil and products made from castor oil contain very little ricin or RCA. However, castor beans are grown for ornamental purposes, too. The seeds from the garden plant present a poisoning hazard to children and pets. Dehydration and vomiting are more dangerous for children than adults, so ingestion of a single castor bean seed may be fatal for a child. However, if the seed is ingested whole, there is a chance that it may pass through the gastrointestinal system without releasing its ricin.
Purified ricin and RCA are of considerable concern as weapons for several reasons. First, castor bean seeds are readily obtainable. Second, several routes of exposure are possible (for ricin: inhalation, injection, or ingestion). Once the proteins are purified, the powdered toxin can be used to contaminate food or beverages. Ricin is heat-stable, so it can be applied to shrapnel within an explosive device. Possibly the greatest concern about ricin used as a weapon is that symptoms of poisoning can readily misdiagnosed.
At present, therapy for ricin poisoning consists of replacing fluids and treating the symptoms of poisoning, but research is underway to develop a vaccine for the toxin. Also, testing is underway for a new drug, using an inactivated form of the ricin protein, to treat individuals following exposure.