The German Commission E monograph suggests that only an ascaridole-free preparation should be used internally. Boldo contains terpene-4-ol, an ingredient similar to that found in juniper, and should be avoided by people with kidney disease, as it could cause kidney irritation.^8,9 In addition, the herb should not be taken during pregnancy or breast-feeding. It should also be avoided by people who have obstruction of the liver bile duct, or severe liver disease.¹⁰ There is one case report of liver damage occurring in a person taking a laxative containing boldo. The herb was suspected, though not proven, to be the cause.¹¹ Excessive use of the herb over long time periods (more than three to four weeks continuously) is not recommended.