Fava Beans are toxic.

I am quoting from 10/10/05 article in WSJ "To Warn or Not to Warn" about favism.

...the occasional consumer of fava beans would grow ill, turn yellow, and develop blood-colored urine. In children, the result often was death.

...during the 1950s, some American doctors, including Dr. Beutler, discovered that the explanation was genetic: These victims were deficient in an enzyme called glucose-6-phosphate dehydrogenase. A certain percentage of people deficient in that enzyme are unable to process fava-bean toxins, which begin destroying red blood cells.
This was a medical rarity - a genetic condition, passed from mother to child. ...this danger is well-known enough in the Mediterranean - where fava beans long have been a dietary staple, and where the genetic mutation is more common than in the U.S. - that in some regions of Italy physicians test children for the enzyme deficiency..