Senna includes herbs, shrubs, and trees. The leaves are pinnate with opposite paired leaflets. The inflorescences are racemes at the ends of branches or emerging from the leaf axils. The flower has five sepals and five usually yellow petals. There are ten straight stamens. The stamens may be different sizes, and some are staminodes. The fruit is a legume pod containing several seed. Senna belongs to a large genus of flowering plants found throughout the tropics, commonly used species being Cassia acutifolio (Alexandrian senna) and C. angustifolio (Indian or Tinnevelly senna). Extracts of the leaves, flowers and fruit of senna have been used for centuries in folk medicine as a laxative and stimulant. Senna is also included in several herbal teas, used for purging and in weight loss. The active components in senna extracts are anthraquinone derivatives and their glucosides, referred to as senna glycosides or sennosides. They appear to act as a local irritant on the colon, which promotes peristalsis and evacuation. Senna may also enhance intestinal fluid accumulation and increase the moisture content of stool by inhibiting electrolyte and water reabsorption from the colon. Senna is minimally absorbed. Senna is used in many over-the-counter laxatives in combination with other agents under trade names such as Ex-lax, Fletcher’s Castoria and Senokot. The typical dose is 15 to 30 mg of sennosides twice a day, but is recommended for short term use only (less than one week). Side effects include abdominal cramps and electrolyte imbalance. Long term use or abuse can lead to “cathartic” colon with diarrhea, cramps, weight loss and darkened pigmentation of the colonic mucosa.