Buckthorn may turn the urine dark yellow or red, but this is harmless. Women who are pregnant or breast-feeding and children under the age of 12 should not use buckthorn without the advice of a physician. Those with an intestinal obstruction, Crohn’s disease or any other acute inflammatory problem in the intestines, diarrhea, appendicitis, or abdominal pain should not use this herb.⁶ Use or abuse of buckthorn for more than ten days consecutively may cause a loss of electrolytes (especially the mineral potassium) or may weaken the colon. Long-term use can also cause kidney damage.⁶