Herbal preparations contain many bioactive compounds with potentially deleterious as well as beneficial effects. There is clearly a need for greater education of patients and doctors about herbal therapy, for legislation to control the quality of herbal preparations, and in particular for further randomized controlled trials to establish the value and safety of such preparations in digestive and other disorders.

– Aliment Pharmacol Ther 2001 Sep;15(9):1239-52 — Review article: herbal treatment in gastrointestinal and liver disease–benefits and dangers. — Langmead L, Rampton DS.

May cause allergic reaction or bloating.
– Dis Colon Rectum 2001 Aug;44(8):1201-9 — Adverse effects of laxatives. — Xing JH, Soffer EE.

Reports have mounted about hepatotoxicity of herbal remedies which ranges from mild liver enzyme alterations to chronic liver disease and liver failure. Hepatotoxic reactions have been observed after the ingestion of Senna.
– Z Gastroenterol 2001 Mar;39(3):225-32, 234-7 — Liver toxicity of drugs of plant origin — Stickel F, Seitz HK, Hahn EG, Schuppan D.

People with the following conditions should not use senna: pain in the abdomen, Crohn’s disease, ulcerative colitis or appendicitis.

– Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 204–8.

Cassia angustifolia (Senna), used as a laxative, is a plant from the Fabaceae family. It includes hydroxyanthracene glycosides, also known as Senna Sennoside. These glycosides stimulate the peristalsis of the colon and alter colonic absorption and secretion resulting in fluid accumulation and expulsion. In the literature, there are reports illustrating the hepatotoxic effects of Cassia angustifolia but there is no report of portal vein thrombosis caused by Cassia Angustifolia. Severe hepatotoxicity senna use is unusual. The cause of senna-related hepatotoxicity is unclear but could be explained by the exposure of the liver to unusual amounts of toxic metabolites of anthraquinone glycosides. Chronic use of Cassia angustifolia may rarely be associated with portal vein thrombosis.

– Clin Toxicol (Phila). 2008 Sep;46(8):774-7.
Portal vein thrombosis related to Cassia angustifolia.Soyuncu S, Cete Y, Nokay AE.