St. John’s Wort

Also indexed as:Hypericum, Hypericum perforatum, Klamath Weed, Saint John’s Wort, St. John's Wort
St. John’s Wort: Main Image© Steven Foster
Common names:
Hypericum, Klamath Weed
Botanical names:
Hypericum perforatum

Side Effects

St. John’s wort has a low incidence of side effects compared to prescription antidepressants. An adverse events profile of St. John’s wort found that, of 14 controlled clinical trials, seven reported no adverse reactions, two had no information, and five reported a total of seven mild reactions.133 Adverse effects reported included stomach upset, fatigue, itching, sleep disturbance, and skin rash. The rate of adverse reactions was always similar to that of the placebo. Additionally, in seven trials comparing St. John’s wort with other antidepressants, the adverse reaction rate for St. John’s wort was consistently lower than that of the antidepressant drugs with which it was compared.

St. John’s wort can make the skin more sensitive to sunlight.134 Therefore, fair-skinned people should be alert for any rashes or burns following exposure to the sun. Three cases of severe blistering and burns were reported in people taking St. John’s wort internally or applying it topically and then being exposed to sunlight.135 There is a case report of a woman experiencing neuropathy (nerve injury and pain) in sun-exposed skin areas after taking 500 mg of whole St. John’s wort for four weeks.136 Although St. John’s wort has photosensitizing properties, the severity of this reaction is not typical for people taking the herb.

People with a history of manic-depressive illness (bipolar disorder) or a less severe condition known as hypomania, should avoid use of St. John’s wort as it may trigger a manic episode.137, 138, 139, 140

There is a single case report in which ingestion of St. John's wort appeared to cause high blood pressure in a 56-year-old man. The blood pressure returned to normal when the herb was discontinued.141

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.

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