Abrin (also known as agglutinin and toxalbumin) is an extremely poisonous protein which is found in the seeds of the rosary pea (Abrus precatorius). The chemical is toxic because it inhibits protein synthesis. Abrin's function as a poison is almost identical to that of ricin, but abrin's toxicity in mice is 75x greater. It was formerly used to treat some chronic eye disorders and it is currently being researched as a potential chemotherapy drug.

Unfortunately, abrin can also be used as a biological warfare agent. When abrin is inhaled, it causes respiratory distress, fever, cough, nausea, tightness in the chest, profuse sweating, the buildup of fluid in the lungs (pulmonary edema), blueness of the skin (cyanosis), and dangerously low blood pressure. If left untreated, it can cause respiratory and cardiovascular failure.

If poisonous amounts of abrin are eaten, it causes nausea, diarrhea, and can cause hemorrhaging in the stomach and intestine and can cause the death of tissues (necrosis) in the liver, spleen, and kidneys.