Herb library · Herb · Hypericum perforatum
St. John's Wort
A yellow-flowered plant sold mostly for low mood. Many studies suggest it may help mild or moderate depression over up to 12 weeks, but it weakens many important medicines, sometimes dangerously.
Serious warning
NCCIH says it has been clearly shown that St. John's wort can interact in dangerous, sometimes life-threatening ways with many medicines, weakening birth control pills, transplant drugs, warfarin, and some HIV, heart, seizure, and cancer drugs. With some antidepressants or other serotonin-affecting drugs it may cause serious side effects.
Traditional use
Widely used in Greek, Islamic, and Chinese medicine; the name refers to John the Baptist, since it blooms around his feast day in late June. Historically it was used for depression, stomach ulcers, colds, and wounds, and its blossoms were steeped in oil to make a red ointment. Today it is sold mainly for depression, and also for menopause symptoms and, on the skin, for wounds.
Traditional energetics
Galenic (hot or cold, dry or moist)
Hot and dry. Culpeper's Complete Herbal (1814), p. 239 (opens in a new tab)
What studies show
- Limited
Mild to moderate depression: many studies suggest it may help, appearing more effective than placebo and about as effective as standard antidepressants. It is uncertain whether this holds for severe depression or beyond 12 weeks.
- Limited
Menopausal hot flashes and somatic symptom disorder: small numbers of studies suggest it may help.
- Insufficient
ADHD, irritable bowel syndrome, OCD, PMS, quitting smoking, and wounds: only a small amount of research on each, and none has clearly shown it helps.
Be careful of
Cautions
- InteractionIt can weaken some antidepressants (such as amitriptyline and bupropion), birth control pills, cyclosporine, phenytoin and carbamazepine, digoxin and ivabradine, indinavir and nevirapine, irinotecan, imatinib and docetaxel, warfarin, and some statins such as simvastatin.
- NoteFor adults taking no medicines it appears safe for up to 12 weeks. Large doses by mouth, or use on the skin, might cause severe skin reactions after sun exposure. Other side effects: diarrhea, dizziness, trouble sleeping, restlessness, skin tingling.
- PregnancyIt may be unsafe in pregnancy because it may raise the risk of birth defects. Breastfed infants of mothers who take it can have colic, drowsiness, and lethargy.
- ConditionDepression can be a serious illness. If you or someone in your family may have depression, see a clinician.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“St. John's wort is an herb abundantly growing in this country and Europe, and proving exceedingly annoying to farmers.”
“The blossoms, infused in sweet oil or bear's oil, by means of exposure to the sun, make a fine, red balsamic ointment for wounds, ulcers, swellings, tumors, etc.”
Sources
- St. John's Wort: Usefulness and Safety (opens in a new tab) · NCCIH · read September 25, 2026
- St. John's Wort (LiverTox) (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.