Herb library · Herb · Frangula alnus (Rhamnus frangula)
Buckthorn bark (alder buckthorn)
The aged bark of the European alder buckthorn, a stimulant laxative closely related to cascara. The EMA accepts it for short-term use in occasional constipation, but it has never been tested in people on its own; its effect is assumed from its chemistry and long use.
Traditional use
A household laxative in Europe for centuries; King's American Dispensatory noted in 1898 that it was "quite popular" with Germans as a laxative, and the EMA's assessment records older European uses for liver and gallbladder complaints, dropsy and scabies. The bark must be dried and stored for about a year before use, because the fresh bark causes vomiting and cramping.
What studies show
No studies in people of this herb on its own yet. What is known of it comes from the traditions that use it.
- Insufficient
Occasional constipation: the EMA recognizes frangula bark for short-term use, but its assessment says the only clinical investigations tested it in combination products and none were controlled. The laxative effect is inferred from its anthraquinone chemistry, expert opinion and experience with related laxatives such as senna.
Be careful of
Cautions
- AmountThe EMA says not to use it for more than 1 week, usually only 2 or 3 times in that week, and only if a change of diet or a fiber (bulk) laxative has not worked. Long-term use of stimulant laxatives can impair bowel function and lead to dependence.
- ConditionDo not use it with intestinal blockage or narrowing, appendicitis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), abdominal pain of unknown cause, or severe dehydration. Not for children under 12. People with kidney disease should watch for electrolyte imbalance.
- InteractionPotassium lost through overuse can strengthen the effect of heart medicines such as digoxin and interact with antiarrhythmics. Diuretics, corticosteroids and licorice root add to potassium loss. Talk with a doctor first if you take any of these or medicines that prolong the QT interval.
- PregnancyThe EMA says not to use it in pregnancy or while breastfeeding. LactMed notes buckthorn laxatives might cause loose stools in breastfed infants.
- NoteFresh or unaged bark causes nausea, cramping and violent vomiting and purging. Use only properly dried, aged bark from a reputable source.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“Nausea, colicky pain, and violent emeto-catharsis are the effects produced by fresh frangula bark. When dried, however, it loses some of its acridity, and then acts as a purgative only.”
Sources
- European Union herbal monograph on Rhamnus frangula L., cortex — Revision 1 (opens in a new tab) · EMA · read September 25, 2026
- Assessment report on Rhamnus frangula L., cortex — Revision 1 (opens in a new tab) · EMA · read September 25, 2026
- Buckthorn (LactMed) (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.