Hypericum: Description, General Use, Clinical Studies, Preparations, Precautions, Side Effects and Interactions

Hypericum perforatum is the most important medicinal species of the genus Hypericum, commonly known as St. John’s wort or Klamath herb.


There are as many as 400 species in the genus, which belongs to the Clusiaceae family. Originally from Europe, St. John’s wort is found throughout the world.

It thrives in sunny fields, open forests, and edges of gravel roads. The first settlers brought this plant to North America. It has become naturalized in the eastern United States and California, as well as in Australia, New Zealand, East Asia, and South America.

As of 2004, St. John’s wort is one of the most widely used herbs in the United States, especially among women.

The whole plant, in particular its round black seeds, gives off a slight turpentine odor. The root with woody branches extends from the base with runners that produce numerous stems.

The simple dark green leaves are veined and grow in opposite pairs, oblong or oval in round branching stems that reach up to 3 feet (91.4 cm).

The tiny holes, visible when the leaf is held in the light, are transparent sebaceous glands that contain a chemical known as hypericin. These characteristic holes inspired the name of the species, Perforatum, which is the Latin word for “perforated.”


The yellow star-shaped flowers, often grouped in three groups, have five petals. The black spots along the margins of the flower contain more hypericin.

The flowers bloom in branched bunches of the flat top on the stems around the summer solstice; it was believed that they contained magical properties that protect the evil spirits.

Its generic name, Hypericum, is derived from a Greek word meaning “on an apparition.” The grass traditionally met on the eve of the summer solstice, on June 23. This date was later celebrated in the Christian church on the eve of the Feast of St. John the Baptist.

This popular custom gave the plant its popular name. The Anglo-Saxon word “herb” means “medicinal herb.”

General use of Hypericum

The herb of San Juan has been known for its medicinal properties already in Roman times. It was a valuable remedy that promoted the healing of traumas and inflammation on the battlefield. The herb is considered vulnerary and can accelerate the healing of wounds, bruises, ulcers, and burns.

It is also popularly used to relieve tension and anxiety, relieve mild depression, and calm women’s mood swings during menopause. The sweet and sour herb is licensed in Germany for use in mild depression, anxiety, and insomnia.

It is said to be helpful in nerve injuries and trauma and was used in the past to accelerate healing after brain surgery. Its antispasmodic properties have been thought to alleviate uterine cramps and menstrual difficulties. St. John’s wort can also be used as an expectorant.

The hypericin in St. John’s wort possesses antiviral properties that are effective against certain cancers. An infusion of the plant taken as tea has helped treat nocturnal enuresis in children.

The oil has been used internally to treat cramping, intestinal worms, and abdominal pain. The medicinal parts of the plant are its leaves and fresh flowers. This herbal remedy has been widely tested in West Germany and is distributed throughout Germany as a folk medicine called Johanniskraut.

Commercially prepared extracts are commonly standardized to contain 0.3% hypericin.

Clinical studies

In contrast to the first 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.

In 2002, health 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 (CNMCA) in the United States published the results of a large-scale study at several sites in April 2002, which reported that St. John’s Wort is not more effective than a placebo for Treat major depression of moderate severity.

The study was also published in the Journal of the American Medical Association. Additional studies carried out in several countries investigate the interactions between St. John’s wort and various prescription drugs.

Prepared with St. John’s wort

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 must be shaken daily.

When the oil absorbs the red pigment, the mixture is poured through muslin or gauze 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 popular culture as the “Oil of Jesus.” This oil forms friction for painful joints, varicose veins, muscular distension, arthritis, and rheumatism.

It can help heal wounds and inflammation and relieve pain from deep bruises when placed in a compress.

An infusion is made by pouring half a liter of boiling water over 1 ounce (28 g) of dried herb or 2 ounces (57 g) of flowers and chopped fresh leaves. Soak in a glass or enamel pot for five to 10 minutes, then strain and cover. The tea must be consumed while it is hot. A general dose is one cup, up to three times a day.

The leaves and flowers are dried and ground with a mortar and pestle in a fine powder to prepare a capsule. The mixture is then placed in gelatin capsules.

The power of the grass varies with the soil, climate, and harvest conditions of the plant. A standardized extract of 0.3% hypericin, commercially prepared from a reliable source, is more likely to yield reliable results.

The standard dosage is up to three 300 mg capsules of 0.3% standardized extract per day.

A tincture is prepared by combining a portion of fresh grass with three parts of alcohol (50% alcohol/water solution) in a glass container. The mixture is placed in a dark place and stirred daily for two weeks.

Then it is slipped through muslin or gauze and stored in a dark bottle. The tincture must maintain its power for two years.

The standard dosage, unless otherwise prescribed, is 0.24 – 1 teaspoon added to 8 oz (227 g) of water, up to three times a day.

An ointment can be prepared by heating 2 ounces (57 g) of oil extract prepared in a double boiler. Once heated, add 1 oz (28 g) of grated beeswax and mix until melted. The mixture is poured into a glass container and allowed to cool. The balm can be stored for up to one year.

The remedy is best maintained if it is refrigerated after preparation. The balm helps treat burns and wounds and relieves painful muscles.

It is also a good skin softener. St John’s wort ointment can be prepared in combination with calendula extract (Calendula officinalis) for application in bruises.


There are several necessary precautions to observe when using St. John’s wort. Pregnant or lactating women should not use the herb at all.

People who take prescription antidepressants should not use St. John’s wort simultaneously since the herb can precipitate a health crisis known as serotonin syndrome.

Serotonin syndrome is life-threatening and is characterized by changes in the level of consciousness, behavior, and neuromotor functioning due to increased levels of the neurotransmitter serotonin in the central nervous system.

Interactions with other medications are the most common cause of serotonin syndrome. Several cases of serotonin syndrome have been reported in patients taking St. John’s wort by themselves or in combination with SSRIs, fenfluramine (Pondimin), or nefazodone (Serzone).

It is also essential for people who use St. John’s wort to buy the herb from a reliable source since the quality of herbal products sold in the United States and Canada varies widely.

A study of 10 popular samples of herbs, including St. John’s wort, reported in 2003 that each herb had “a wide range of ingredients in labels and recommended daily doses (DDR) among the available products.”

The researchers recommended that doctors and consumers pay close attention to over-the-counter (OTC) herbal product labels.

In addition to the potential risks of the herb to humans, it can be toxic to livestock. Harmful effects in livestock include reports of edema of the ears, eyelids, and face due to photosensitization after the animal eats the grass. Exposure to sunlight activates hypericin in the plant.

Adverse effects have been reported in horses, sheep, and pigs, including a fantastic gait and blistering or peeling skin. Smaller animals, such as rabbits, suffer serious side effects from the accidental ingestion of St. John’s wort.

The Association of Veterinary Botanical Medicine (AMBV), which was founded in 2002 as a branch of the American Veterinary Medical Association (AMVA), offers a page on its website to report the adverse effects of St. John’s wort or any other herb in cats, dogs or other animals.

Side effects of Hypericum

When used internally or externally, the herb can cause photodermatitis in humans with clear or sensitive skin after exposure to sunlight or other ultraviolet light sources. Some case reports have also reported side effects in breastfeeding women taking hypericum extract.

Changes have been reported in the nutritional quality and taste of milk and the reduction or cessation of breastfeeding. In addition, it is known that St. John’s wort causes headaches, stiff neck, nausea or vomiting, and high blood pressure in susceptible individuals.


The herb of San Juan has a series of problematic interactions with many drugs. It has been reported to interact with amphetamines, inhalants for asthma, decongestants, diet pills, narcotics, tryptophan, tyrosine (amino acids), antidepressant medications, and certain foods.

It has also been reported to interfere with the effectiveness of contraceptive pills and indinavir (Crixivan), and other AIDS medications.

In addition, anesthesiologists reported that the herb increases the bleeding time in patients under general anesthesia. Patients should always consult a conventional health professional before using St. John’s Wort and stop taking it at least two weeks before major surgery.