St. John’s wort

St. John’s wort
St. John’s wort

Hypericum perforatum is the most medicinally important species of the Hypericum genus, commonly known as St. John’s wort or Klamath weed. There are as many as 400 species in the genus, which belongs to the Clusiaceae family. Native to Europe, St. John’s wort is found throughout the world. It thrives in sunny fields, open woods, and gravelly roadsides.

Early colonists brought this plant to North America, and it has become naturalized in the eastern United States and California, as well as in Australia, New Zealand, eastern Asia, and South America. As of 2004, St. John’s wort is one of the most commonly used herbs in the United States, especially among women.

The entire plant, particularly its round black seeds, exudes a slight turpentine-like odor. The woody-branched root spreads from the base with runners that produce numerous stalks.

The simple dark green leaves are veined and grow in opposite, oblong, or oval pairs on round branching stalks that reach as high as 3 ft (91.4 cm). Tiny holes, visible when the leaf is held to the light, are actually transparent oil glands containing a chemical known as hypericin.

These characteristic holes inspired the species name, Perforatum, which is the Latin word for “perforated.” The bright yellow star-shaped flowers, often clustered in groups of three, have five petals. Black dots along the margins of the blossom contain more hypericin.

The flowers bloom in branching flat-topped clusters atop the stalks, around the time of the summer solstice. St. John’s wort, sometimes called devil’s flight or grace of God, was believed to contain magical properties that ward off evil spirits. Its generic name, Hypericum, is derived from a Greek word meaning “over an apparition.”

The herb was traditionally gathered on midsummer’s eve, June 23. This date was later celebrated in the Christian Church as the eve of the feast day of St. John the Baptist. This folk custom gave the plant its popular name. The Anglo-Saxon word “wort” means “medicinal herb.”

General use

St. John’s wort plant
St. John’s wort plant
St. John’s wort has been known for its medicinal properties as far back as Roman times. On the battlefield, it was a valued remedy that promoted healing from trauma and inflammation. The herb is regarded as a vulnerary, and can speed the healing of wounds, bruises, ulcers, and burns.

It is also popularly used as a nervine for its calming effect, easing tension and anxiety, relieving mild depression, and soothing women’s mood swings during menopause. The bittersweet herb is licensed in Germany for use in mild depression, anxiety, and sleeplessness.

It is said to be helpful in nerve injury and trauma, and was used in the past to speed healing after brain surgery. Its antispasmodic properties have been thought to ease uterine cramping and menstrual difficulties. St. John’s wort may also be used as an expectorant.

The hypericin in St. John’s wort possesses antiviral properties that are said to be effective against certain cancers. An infusion of the plant taken as a tea has been helpful in treating bedwetting in children. The oil has been used internally to treat colic, intestinal worms, and abdominal pain.

The plant’s medicinal parts are its fresh leaves and flowers. This herbal remedy has been extensively tested in West Germany, and is dispensed throughout Germany as a popular medicine called Johanniskraut. Commercially prepared extracts are commonly standardized to contain 0.3% hypericin.

Clinical studies

In contrast to early European reports made in the 1980s, more recent clinical studies tend to undermine the claims made for St. John’s wort as a possible treatment for HIV infection and depression. As of 2002, health care professionals and regulatory agencies in Europe were advised to warn AIDS patients that St. John’s wort decreases the effectiveness of drugs known as HIV protease inhibitors.

In addition, the National Center for Complementary and Alternative Medicine (NCCAM) in the United States released the results of a large-scale multi-site study in April 2002, which reported that St. John’s wort is no more effective than a placebo for treating major depression of moderate severity.

The study was also published in the Journal of the American Medical Association. Additional studies being conducted in several countries are researching the interactions between St. John’s wort and various types of prescription medications.


An oil extract can be purchased commercially or prepared by combining fresh St. John’s wort flowers and leaves in a glass jar with sunflower or olive oil. The container should be sealed with an airtight lid, and placed on a sunny windowsill for four to six weeks.

It should be shaken daily. When the oil absorbs the red pigment, the mixture is strained through muslin or cheesecloth, and stored in a dark container. The medicinal oil maintains its potency for two years or more.

The oil of St. John’s wort has been known in folk culture as “Oil of Jesus.” This oil forms a rub used for painful joints, varicose veins, muscle strain, arthritis, and rheumatism. Placed in a compress, it can help to heal wounds and inflammation, and relieve the pain of deep bruising.

An infusion is made by pouring one pint of boiling water over 1 oz (28 g) of dried herb, or 2 oz (57 g) of fresh, minced flower and leaf. It is steeped in a glass or enamel pot for five to 10 minutes, then strained and covered. The tea should be consumed while it is warm. A general dose is one cup, up to three times daily.

To prepare a capsule, the leaves and flowers are dried, and ground with a mortar and pestle into a fine powder. The mixture is then placed in gelatin capsules. The potency of the herb varies with the soil, climate, and harvesting conditions of the plant.

A standardized extract of 0.3% hypericin extract, commercially prepared from a reputable source, is more likely to yield reliable results. Standard dosage is up to three 300 mg capsules of 0.3% standardized extract daily.

A tincture is prepared by combining one part fresh herb to three parts alcohol (50% alcohol/water solution) in a glass container. The mixture is placed in a dark place, and shaken daily for two weeks.

Then it is strained through muslin or cheesecloth, and stored in a dark bottle. The tincture should maintain potency for two years. Standard dosage, unless otherwise prescribed, is 0.24–1 tsp added to 8 oz (227 g) of water, up to three times daily.

A salve can be made by warming 2 oz (57 g) of prepared oil extract in a double boiler. Once warmed, 1 oz (28 g) of grated beeswax is added and mixed until melted. The mixture is poured into a glass jar and allowed to cool. The salve can be stored for up to one year.

The remedy keeps best if refrigerated after preparation. The salve is useful in treating burns, wounds, and soothing painful muscles. It is also a good skin softener. St. John’s wort salve may be prepared in combination with calendula extract (Calendula officinalis) for application on bruises.


There are a number of important precautions to observe in using St. John’s wort. Pregnant or lactating women should not use the herb at all. Persons taking prescription antidepressants of any kind should not use St. John’s wort at the same time, as the herb may precipitate a health crisis known as serotonin syndrome.

Serotonin syndrome is potentially life-threatening, and is characterized by changes in level of consciousness, behavior, and neuromotor functioning as a result of increased levels of the neurotransmitter serotonin in the central nervous system. Drug interactions are the most common cause of serotonin syndrome.

Several cases of serotonin syndrome have been reported in patients who were taking St. John’s wort by itself or in combination with SSRIs, fenfluramine (Pondimin), or nefazodone (Serzone). Persons using the herb should discontinue it a minimum of two weeks prior to any surgery requiring general anesthesia, as it interacts with a number of intravenous and inhaled anesthetics.

It is also important for persons using St. John’s wort to purchase the herb from a reputable source, as the quality of herbal products sold in the United States and Canada varies widely.

Saved St. John’s wort
Saved St. John’s wort
One study of 10 popular herb samples, including St. John’s wort, reported in 2003 that each herb had "a large range in label ingredients and recommended daily dose (RDD) across available products." The researchers recommended that physicians and consumers pay very close attention to labels on over-the-counter (OTC) herbal products.

In addition to the herb’s potential risks to humans, it can be toxic to livestock. Toxic effects in cattle include reports of edema of the ears, eyelids, and the face due to photosensitization after the animal eats the herb.

Exposure to sunlight activates the hypericin in the plant. Adverse effects have been reported in horses, sheep, and swine, including a staggering gait and blistering or peeling of the skin. Smaller animals, such as rabbits, suffer severe side effects from accidental ingestion of St. John’s wort.

The Veterinary Botanical Medicine Association (VBMA), which was founded in 2002 as an offshoot of the American Veterinary Medical Association (AVMA), offers a page on its website for reporting adverse effects of St. John’s wort or any other herb in cats, dogs, or other animals.

Side effects

When used either internally or externally, the herb may cause photodermatitis in humans with fair or sensitive skin, following exposure to sunlight or other sources of ultraviolet light. There have also been some case reports of side effects in breast-feeding women taking hypericum extract.

Changes in the nutritional quality and flavor of the milk, as well as reduction or cessation of lactation, have been reported. In addition, St. John’s wort has been known to cause headaches, stiff neck, nausea or vomiting, and high blood pressure in susceptible individuals.


St. John’s wort has a number of problematic interactions with many drugs. It has been reported to interact with amphetamines, asthma inhalants, decongestants, diet pills, narcotics, tryptophan and tyrosine (amino acids), as well as antidepressant medications and certain foods. It has also been reported to interfere with the effectiveness of birth control pills as well as with indinavir (Crixivan) and other AIDS medications.

Moreover, anesthesiologists have reported that the herb increases bleeding time in patients under general anesthesia. Patients should always consult a mainstream health practitioner before using St. John’s wort, and should discontinue taking it at least two weeks prior to major surgery.