Do not confuse blessed thistle with its cousin, milk thistle Cardus marianus, they are two entirely different plants, despite the fact that they share a common name (holy thistle), and both are known for supporting the liver. Blessed thistle and its close cousin, milk thistle, are both excellent tonics for the liver and digestion. Both are know to repair damaged liver cells. A distinctive bitter, blessed thistle can be used as a digestive aid before meals. It is diuretic and induces sweating. Used as a poultice or compress, the plant has a reputation for curing chilblains. ^{Mabey, Richard ,40} The herb is often used in combination with other estrogenic herbs to treat menstrual difficulties. One of the main uses in traditional herbal medicine is of a galactaloge, an herb that stimulates mother's milk.

Medieval monks held this plant in high esteem, as the name suggests and considered it a cure for everything from smallpox to headaches, being supposed to even cure the plague. It has been stated that the herb was first cultivated by Gerard in 1597, but as this book was published twenty years previously it would appear to have been in cultivation much earlier, and in fact is described in the Herbal of Turner in 1568. ^{(Grieve, M.)}