Senna is an ingredient in several commercial laxative products. It contains chemicals that belong to the class known as anthraquinones, which are further categorized as stimulant laxatives. They work by irritating the lining of the lower gastrointestinal tract. The resulting contractions of the bowel act to push out material in the lower intestinal tract. Anthraquinones may also keep more water in intestinal contents, thereby producing a softer stool that is usually easier to pass. Senna laxatives may take 8 to 12 hours to produce results.
In animal studies, senna has not shown negative effects on pregnant animals or their offspring. Although a very small amount of senna passes into human breast milk, the amounts are not enough to cause diarrhea in infants. Senna-containing laxatives are often given to relieve constipation for pregnant and breast-feeding women, the elderly, surgery patients, and individuals who are taking narcotic pain medications which frequently cause constipation as a side effect. Children under the age of 5 should not be given senna, however, due to the possibility that it may cause a skin rash.