Cramp bark comes from the guelder-rose shrub (Viburnum opulus) and has a long history in traditional European herbalism. Compounds in the bark help relax smooth muscle spasms in the uterus and digestive tract.
People take it as a tea, tincture, or extract during menstrual cramps or digestive pain that feels crampy.
Avoid cramp bark if you are pregnant or breastfeeding. Safety in those situations remains unproven. Drug interaction data is scarce, so use caution if you take any antispasmodic medication.