Blessed thistle is a small, annual herb native to the Mediterranean and naturalized in North America, where it is often regarded as a noxious weed. The herb is a member of the family Asteraceae, which contains the second largest number of flowering plants, and is the only species in the genus Cnicus. Other names for the plant include holy thistle, St. Benedict's thistle and spotted thistle. Blessed thistle should not be confused with milk thistle. Despite their similar names, they are two completely different plants.
In appearance, blessed thistle is similar to other types of thistle, but can still be identified by its own unique features. The characteristic hairy stems and spiny-edged leaves are present, but the herb also produces bright yellow flowers surrounded by spiny bracts, or specialized leaves meant to attract pollinators. The plant's leaves can reach up to 12 inches (30.5 centimeters) in length and 3 inches (7.6 centimeters) in diameter. The entire blessed thistle plant can reach up to 24 inches (61 centimeters) in height.
Blessed thistle was used extensively for medicinal purposes during the medieval period in Europe, where it was considered a cure for just about every ailment. Today, many of the herb's traditional uses are still practiced by herbalists and natural health practitioners. It is one of the oldest folk remedies for treating amenorrhea, or the absence of the menstrual cycle, and is often used in commercial herbal preparations formulated for women. The plant is also believed to stimulate bile production in the liver, and is used to treat liver disorders of all types. Other modern medicinal uses of blessed thistle include regulating the menstrual cycle, improving appetite, lowering fevers and treating indigestion.
The blessed thistle plant is not considered edible, unlike many other types of thistle, as it has an extremely bitter taste. It may be taken internally, however, in the form of capsules or as an extract. The herb may also be made into a tea, although other aromatic herbs should be added to reduce the bitter flavor. The recommended dosage for use as a home herbal remedy is two 360-milligram capsules up to three times per day, or 10 to 20 drops of liquid extract dissolved in water three times per day. Tea is made by steeping 2 teaspoons (9.86 milliliters) of the dried herb in 8 ounces (236 milliliters) of boiling water for 10 to 15 minutes.
Although blessed thistle is generally safe for consumption when taken as directed, large doses can cause upset stomach and vomiting. This is more common when taking tea made from the herb, as it is harder to regulate the amount of plant material consumed. For the best results, no more than two cups of tea should be taken per day. Individuals with stomach ulcers should avoid taking the herb in any form, as it can cause gastric irritation that worsens the condition.