The Common Rue (Ruta graveolens), also known as Herb-of-Grace, is a species of rue grown as a herb. It is native to the Balkan Peninsula, southeastern Europe. It is sometimes grown as an ornamental plant in gardens, especially because of its bluish leaves, and also sometimes for its tolerance of hot and dry soil conditions. It also is cultivated as a medicinal herb, as a condiment, and to a lesser extent as an insect repellent. The caterpillars of the Papilio machaon butterfly species feed on rue, among other kinds of plants. Ruta graveolens is also used in Brazil as the key ingredient in homemade herbal cough syrup, when mashed with caramelized sugar and honey. Exposure to Common Rue, or herbal preparations derived from it, can cause severe phytophotodermatitis which results in burn-like blisters on the skin. Ruta graveolens belonging to family Rutaceae has long been traditionally used as a medicinal plant as well as a flavoring agent in food.