Holy (Blessed) Thistle has been used medicinally for over 2000 years, most commonly for the treatment of liver problems by supporting it in the release of toxins. It has been highly regarded for therapeutic uses and was cultivated throughout Europe and some say gained its moniker through its reputation as a 'heal-all', even credited with curing the Plague. It was in known cultivation as early as the mid-1500's.

In "Much Ado About Nothing", Shakespeare praises its medicinal prowess: "Get you some of this distilled Carduus Benedictus and lay it to your heart; it is the only thing for a qualm.... I mean plain Holy Thistle... Therefore I counsell all that have Gardens to nourish it, that they may have it always to their own use, and the use of their neighbours that lacke it."

Mattheolus and Fuschius wrote of Carduus benedictus, saying "It is a plant of great virtue; it helpeth inwardly and outwardly; it strengthens all the principal members of the body, as the brain, the heart, the stomach, the liver, the lungs and the kidney; it is also a preservative against all disease, for it causes perspiration, by which the body is purged...therefore, give God thanks for his goodness, Who hath given this herb and all others for the benefit of our health."

Holy thistle products are still popular in Europe and the United States for various types of liver disease. Holy thistle is believed to have great power in the purification and circulation of the blood. It is such a good blood purifier that drinking a cup of thistle tea twice a day will cure chronic headaches. It is also used for stomach and digestive problems, gas in the intestines, constipation, gallbladder disorders, lack of appetite (not feeling hungry) and on the skin for treating infected wounds or ulcers. As well it is very effective for dropsy, strengthens the heart and is good for the lungs and kidneys. Some claim that the warm tea, made from Holy Thistle, given to mothers will produce a good supply of milk. That is why it is also called Milk Thistle. It is also said to be good for girls entering womanhood as a tonic.

In herbal medicine today, Holy Thistle is used to treat cancer as well as infections, heart and liver ailments, and fevers.