orris oil, yellowish semisolid fragrant essential oil obtained from the rhizomes of the Florentine iris (Iris germanica). Orris oil has a warm violetlike odour and is used in perfumes and lotions. Although the oil was once popular in candies, soft drinks, and gelatin desserts, its use in edible goods has declined because of the risk of allergic reactions in some people. The oil was formerly used to treat bronchitis, edema, and liver ailments and is sometimes still used as a traditional medicine.