Side effects of St. John’s wort

As a natural remedy, St. John’s wort usually shows good tolerance. Side effects occur only rarely. Patients with high-dose, internal therapy with St. John’s wort (for depression) often show increased sensitivity to sunlight.

This is due to the active ingredient hypericin, which increases the skin’s sensitivity to UV light. In the case of prolonged sunbathing, sunburn-like skin reactions are to be feared. In addition, patients frequently report complaints in the gastrointestinal tract in the course of a high-dose therapy with St. John’s wort.

Diarrhea and stomach cramps are possible. In rare cases, nausea and loss of appetite may also occur. When St. John’s wort is used externally, side effects are very rare.

Allergic reactions to various ingredients of St. John’s wort oil or other St. John’s wort containing products are possible. These usually manifest themselves in the skin area. Swelling and redness of the skin may occur.

Patients often report accompanying an inner restlessness and an increased feeling of tiredness. When using St. John’s wort therapy, it should be borne in mind that there can be numerous interactions when it is combined with other medications. Depending on the preparation, these can be noticed by different symptoms and can be mistakenly interpreted as side effects of St. John’s wort.

In the following, side effects of St. John’s wort in various areas of application are explained in detail. In addition to the active ingredients hyperforin and hypericin, St. John’s wort contains numerous other ingredients, some of which act in the liver area. These increase the activity of various enzymes in the liver (so-called cytochrome P450 monooxygenases), which are significantly involved in the metabolic processes of the liver.Among other things, these enzymes lead to the activation and degradation of numerous toxic substances and drugs.

This can lead to considerable interactions when St. John’s wort is combined with other medicines. However, the liver is not normally damaged by this – on the contrary, by stimulating the liver metabolism, the liver is strengthened in its effectiveness. Patients frequently report various symptoms in the eye area in the course of a high-dose therapy with St. John’s wort.

Often these symptoms initially become noticeable by a constant burning sensation in the eyes. At the same time, the eyelids may be slightly swollen. An increased sensitivity to light during St. John’s wort treatment can also manifest itself in the area of the eyes.

There is an increased risk of developing conjunctivitis (inflammation of the conjunctiva). At the same time, the risk of clouding of the eye lenses (cataracts) is increased with long-term therapy with St. John’s wort. Patients should therefore protect their eyes from intense sunlight during treatment.

Another serious side effect that can occur with a high-dose, internal therapy with St. John’s wort is the so-called serotonin syndrome. As already mentioned, St. John’s wort leads to an increase in the concentration of serotonin in the central nervous system. Very high doses (or overdoses) can cause symptoms typical of high serotonin levels.

Classically, these include dizziness and clouding of consciousness. Also involuntary twitching of the muscles, anxiety and a general feeling of illness are often noticed. Serotonin syndrome is a very serious side effect, which in extreme cases can also lead to loss of consciousness and coma.

It should be noted that, in addition to St. John’s wort, numerous other drugs can also cause an increased concentration of serotonin in the CNS and this typical symptomatology. For this reason, these drugs must not be administered in combination with St. John’s wort. As a herbal medicine, St. John’s wort is used today mainly for its slightly mood-lifting effect for the treatment of mild to moderate depression, winter depression or nervous restlessness.

St. John’s wort can be used externally as well as internally. For external use, it is used in oily concentration for injuries and burns. It is believed that the flavonoid content of St. John’s wort has an anti-inflammatory effect when used externally.

The antidepressant and nerve-soothing effect can be attributed to an influence on messenger substances (=transmitters) of the brain, which could be determined for several of the contained ingredients of St. John’s wort. However, St. John’s wort can only have this effect when used internally. By influencing messenger substances it is used in the therapy of depression. All in all, the medicinal plant is considered a useful alternative treatment for mild depression. However, since St. John’s wort interacts with other medications, it should not be taken without consulting the treating physician!