What Is Cnicus Benedictus?

Cnicus benedictus, also called blessed thistle, holy thistle or Saint Benedict thistle, is an annual herb that is native to Asia and Europe but is widely cultivated throughout the United States. All parts of the plant are used to create herbal supplements. Blessed thistle contains chemicals that might have medicinal properties.

This herb was well-known and its uses were widely documented during the Middle Ages. Herbalists recommended it to patients who were suffering from gout, stomach upset and fever, among other uses. Some physicians of the period even thought it might be useful in treating the plague, and monks administered it as a treatment for smallpox.

Cnicus benedictus plants contain chemicals called sesquiterpene lactones or cnicin, as well as mucilage, alkaloids, tannins and volatile oil. The herb might have anti-inflammatory features. Some herbalists think that it helps stimulate gastric juices and saliva, which improves the digestion.

Some nursing mothers drink a tea made from the Cnicus benedictus herb to stimulate the flow of breast milk. Menopausal women use it to help regulate heavy periods. It might also be useful for triggering delayed menstrual cycles.

Blessed thistle might be useful for stimulating slow or sluggish livers. Some individuals use the herb as an expectorant, and others apply it externally as an antiseptic treatment for cuts or burns. It might also help treat chronic headaches or lethargy.

The plant chemical cnicin is used as an ingredient in alternative cancer treatment medications. In theory, the chemical acts against existing cancer cells and stops new cancer cells from forming. Blessed thistle seeds might also have anti-fungal properties.

This herb has few serious side effects. Women who are pregnant should avoid blessed thistle, and nursing mothers should use it only under a doctor's supervision. People who are allergic to ragweed might have an allergic reaction to Cnicus benedictus; individuals who suffer from Crohn's disease or other inflammatory digestive problems should also avoid this herb, because it can further irritate the stomach.

As of 2011, there were no known interactions between Cnicus benedictus and any foods or other herbs. Blessed thistle increases stomach acids, so it might lessen the benefits of medications that are designed to decrease stomach acids. People who ingest too much of the herb might also suffer from upset stomach, nausea or vomiting.

The Cnicus benedictus plant grows about 2 feet (about 61 cm) tall. It has a hairy, multi-branched stem covered in spiny, woolly, deeply lobed foliage. Yellowish-red spines surround a yellow flower head.