There are some 400 species of Senna, which are mostly natives of the Indian subcontinent. Collectively they are often referred to as Cassia senna. The pods have been used as an effective and reliable laxative for thousands of years and played an important part in Arabian medicine since the 9th century, where it was imported along with dozens of spices from India and China. Ayurveda and Chinese medicine made the broadest use of Senna, employing not only the pods, but also the leaves for numerous purposes. Due to its purgative properties it is sometimes included in modern weight-loss programs, but this use is not recommended, as it is habit forming.
Cassia's action depends on irritating the intestinal tract, which causes the muscles to contract and thus produces a bowel movement. It also binds liquids in the intestines. In Ayurveda it is also used externally for certain skin problems, jaundice, bronchitis and anaemia. In Chinese medicine it is used to 'cool the fire of the liver'. Senna leaves can have a very drastic effect. It is best not to boil or simmer them, as this releases substances that produce a cathartic action. The best way to prepare Senna is either to steep a few pods in warm water for 6-10 hours, or infuse with simmering water, allow to cool and drink the liquid without the suds. Senna (especially the suds) may cause griping. It can be combined with Ginger and other digestive relaxants to reduce this cramping effect. Do not use during pregnancy or while breastfeeding.
Senna pods are sometimes included in sachets used as love charms.