Shepherd's purse, also known as lady's purse, pickpocket, witches' pouches and various other common names, is a European native now naturalized as a wayside weed throughout the world. Its botanical name, Capsella bursa-pastoris, literally translates from Latin to mean "purse of the shepherd," and is a reference to the flat, heart-shaped seed capsules that resemble tiny purses. Shepherd's purse tea is a traditional remedy for excessive bleeding, but is not without potential side effects.
The raw material to make shepherd's purse tea should not contain the seeds of the plant since they contain cardioactive steroid compounds that, according to the "Physician's Desk Reference for Herbal Medicines," may unpredictably lower or raise blood pressure. In addition, Mark Blumenthal, editor of "Herbal Medicine: Expanded Commission E Monographs," says that large doses of these steroid compounds may increase heart rate or induce heart palpitations.
The presence of fumaric acid in the herb has been shown to be effective in treating psoriasis. This substance also appears to inhibit tumor growth in mice, according to a study published in the June 1976 issue of Cancer Research. Unfortunately, another study published in the August 2003 issue of The British Journal of Dermatology also showed that fumaric acid therapy may lead to an increased risk of lymphocytopenia, a rare disorder in which the level of white blood cells significantly decreases. In fact, the researchers noted that out of 66 psoriasis patients treated with fumaric acid, 76 percent developed some degree of lymphocytopenia and four patients were forced to permanently discontinue therapy.
The "Physicians' Desk Reference for Herbal Medicines" also says that shepherd's purse frequently serves as a host to various fungi, such as Candida albicans, which means that tea preparations may contain mytoxins that are capable of causing disease by attacking the immune system. (Reference 1)
The "Physician's Desk Reference for Herbal Medicines" warns that you should not drink shepherd's purse tea if you are pregnant since compounds in this herb increase uterine contractions and may cause miscarriage. This caution applies to nursing women as well, since it is not known if the compounds in this herb are passed through breast milk.
Long-term use or drinking excessive amounts of the tea may increase the effects of sedative drugs and interfere with blood pressure and thyroid medications. Finally, if you have a history of heart problems, kidney stones or kidney disease, you should avoid shepherd's purse.