St. John’s Wort (Hypericum perforatum)

Herbe aux mille trous — St. John’s Wort

1. Folklore and Traditions

A quintessential solar plant in Celtic and Germanic traditions, St. John’s Wort was one of the “Simples,” the medicinal plants traditionally cultivated in monastery gardens during the Middle Ages. Since the Gallo-Roman period, it has also been known as “Chasse-Diable” (“devil chaser”), based on the belief that it could ward off evil spirits and protect homes.

Its flowering period, which coincides with the summer solstice and the feast of St. John, reinforced its sacred character. According to tradition, St. John’s Wort was to be harvested on June 24 at noon, when the sun was at its highest point and the plant was believed to possess its full power.

Bouquets were then hung over the doors of homes, in windows, or in barns to protect the household, family, and animals, while also promoting prosperity and abundant harvests. In Celtic countries, it was believed to bring peace, health, and fertility to the entire household.

The bouquet remained in place throughout the year before being burned at the following St. John’s celebration and replaced with a new one. This gesture symbolized the renewal of the cycle of protection for the coming year.

It was also common to carry a few sprigs of the plant during the night of St. John or to pass them over the flames of the bonfire. Having become a protective amulet, it was believed to ward off harmful influences and attract good fortune until the following solstice.

2. The Main Active Constituents

St. John’s Wort is a fascinating plant because its activity relies primarily on two very different compounds: hypericin and hyperforin.

For a long time, hypericin was believed to be responsible for most of the plant’s effects. It was not until the 1970s that researchers discovered hyperforin, which is now recognized as the main compound involved in its antidepressant activity.

Hypericin: the red pigment

Hypericin is the pigment responsible for turning St. John’s Wort oil a beautiful ruby red after several weeks of maceration.

Its main properties include:

• Antiviral
• Antidepressant
• Responsible for photosensitivity following oral ingestion: once absorbed through the intestines and carried through the bloodstream to the skin, hypericin can react to UV radiation and increase sensitivity to sunlight.

Contrary to a widespread belief, documented cases of photosensitization primarily involve animals, particularly sheep and cattle, that have consumed large quantities of fresh plant material. To date, the available evidence does not clearly demonstrate that St. John’s Wort oil applied to the skin causes photosensitivity in humans.

Hypericin is relatively stable when protected from light and properly dried. It is poorly soluble in water, which explains why teas contain very little of it, whereas it is extracted more effectively into oil and alcohol-based preparations.

Hyperforin

Hyperforin is now considered the main antidepressant compound in St. John’s Wort.

Its mechanism is particularly interesting because it simultaneously inhibits the reuptake of several neurotransmitters, including serotonin, dopamine, and norepinephrine.

This type of mechanism is relatively uncommon in the plant world.

Unlike hypericin, hyperforin is extremely unstable. It oxidizes rapidly when exposed to air and degrades under the influence of light.

3. Red Oil: A True Therapeutic Treasure

St. John’s Wort oil is probably the most remarkable traditional preparation made from this plant.

Its main external uses include:

• Powerful anti-inflammatory: muscle pain, tendinitis, bruises, joint pain, and burns
• Nerve repair and support: sciatica, neuralgia, post-herpetic nerve pain, nerve trauma, and inflammation along the path of a nerve
• Soothing for the skin: sunburn, irritation, and superficial burns

In traditional herbalism, it is applied directly along the path of painful nerves to support their recovery.

Contrary to a widespread belief, its external use for sunburn has been part of traditional practice for a very long time. Warnings regarding photosensitivity mainly stem from observations following oral ingestion of the plant and do not appear to apply in the same way to oil used topically.

4. Tea: A Gentle Preparation

St. John’s Wort tea is not ineffective; it simply extracts a different family of constituents. It is rich in flavonoids but very low in hyperforin (which is practically absent) and contains only very small amounts of hypericin. This is why its properties differ from those of a tincture, an oil, or a standardized extract.

Flavonoids are powerful natural antioxidants. They also possess anti-inflammatory, neuroprotective, and mildly relaxing properties. They help protect cells from oxidative stress and support circulation.

Studies demonstrating effectiveness for mild to moderate depression have been conducted almost exclusively using standardized extracts rich in hyperforin and hypericin, rather than infusions.

5. Drug Interactions — Internal Use

St. John’s Wort is one of the medicinal plants associated with the greatest number of drug interactions.

The main mechanism involves induction of cytochrome P450 enzymes (CYP3A4) as well as certain transport proteins such as P-glycoprotein.

In simple terms, St. John’s Wort stimulates certain liver enzymes responsible for breaking down medications. As a result, medications may be eliminated much more quickly, which can significantly reduce their effectiveness.

The best-documented interactions include:

• Oral contraceptives
• Anticoagulants
• Immunosuppressants (e.g., cyclosporine)
• HIV medications
• Several medications used in oncology
• Certain antiepileptic drugs

Antidepressants are different!

In this case, the risk does not primarily involve the liver, but rather the additive effects on serotonin, which may contribute to serotonin syndrome.

As a precaution, St. John’s Wort should never be taken internally at the same time as a medication without first consulting a healthcare professional.

Serotonin syndrome: An excess of serotonin in the nervous system that can occur when St. John’s Wort is combined with certain antidepressants. This interaction can cause a potentially serious reaction requiring medical evaluation.

Hyperforin

Current evidence suggests that hydroalcoholic maceration may help protect hyperforin from degradation, probably by limiting its exposure to oxygen and keeping it within the plant matrix. However, few studies have quantitatively evaluated this protective effect in homemade preparations.

© 2026 Mélanie Lavoie — La Prêle du Temps. Any reproduction must credit the source and obtain permission from the author.