Rue (Ruta graveolens), also called common rue, herb-of-grace, and tena adam in Ethiopia, is an herb cultivated worldwide as an ornamental, but it is rarely now used for cooking. This is in part because it has some bitterness and causes stomach discomfort in some people.
In Ethiopia, where it is known as tena adam (lit. "Health for Adam") rue is still widely used as an herb. Ground rue fruits are an ingredient in berbere spice powder, and rue leaves are sometimes dipped into coffee or infused to make kuti.
In large or concentrated doses, rue becomes toxic. It can cause gastric pain, vomiting, and death. It can also cause burn-like blisters on the skin when exposed to sunlight. (The author speculates that this phytophotodermatitis may be the underlying cause of the phenomenon of mech sores reported by Harry Kloman (see refs); the presence of rue in berbere may sensitize the skin of the lips and cause blistering when diners are quickly exposed to sunlight)