Cramp bark, also known as Viburnum opulus, is a plant native to Europe and North America, the bark of the plant is used for medicinal purposes. It has been traditionally used to help relieve muscle spasms and cramps, particularly in the uterus and gastrointestinal tract. It is also used to help reduce menstrual cramps and to help alleviate symptoms of premenstrual syndrome (PMS). It has been traditionally used to help reduce anxiety and to help improve sleep. Cramp bark is also believed to have anti-inflammatory properties and may help to reduce pain and inflammation.