St. John's Wort

What Should I Know About It?

St. Johns Wort, close-up
Maximilian Stock Ltd./Photographer's Choice/Getty Images

What is St. John’s Wort?

St. John’s wort (Hypericum perforatum) is a plant used in herbal medicine. A shrubby perennial plant with bright yellow flowers, St. John's wort was named because the flowers were said to bloom for the first time around June 24, the birthday of St. John the Baptist. The word "wort" means "plant" in Old English.

St. John’s wort has long been used as a folk remedy for emotional disorders.

It was once thought to rid the body of evil spirits. An oil made from St. John’s wort has also been used for wound healing and for a variety of other conditions.

Uses for St. John’s Wort

In alternative medicine, St. John’s Wort is said to help with the following health concerns:

Benefits of St. John’s Wort

Here’s a look at the possible health benefits of St. John’s Wort:

1) Mild to Moderate Depression

According to research, St. John’s wort may be as effective as prescription drugs in the short-term (1-3 months) for treating mild to moderate depression. Found to be more effective than a placebo, St. John’s wort has been found to be as effective as low-dose tricyclic antidepressants, tetracyclic antidepressants, and selective serotonin reuptake inhibitors (SSRIs) such as sertraline (Zoloft@), fluoxetine (Prozac@), and paroxetine (Paxil@).

It appears to improve mood and decrease related symptoms such as anxiety and insomnia. 

Although people sometimes turn to St. John's wort as a more tolerable alternative to antidepressant drugs (which may have side effects such as tiredness, sexual dysfunction, mental fogginess), St. John's wort can also have significant side effects (particularly for people who take other medication or have other health conditions) and it can greatly increase the risk of phototoxic skin reactions even when taken at therapeutic doses (see page 2 of this article for more information).

Two recent studies in psychiatric care settings have not found St. John’s wort to be effective for major depression or other disorders, such as seasonal affective disorder. 

The majority of studies on St. John’s wort and depression have used extracts that have been standardized to the hypericin content, however, extracts standardized to hyperforin have also found to be effective.

Related: 8 Natural Depression Remedies to Consider.

2) Menopausal Symptoms

St. John’s wort in combination with the herb black cohosh may help to alleviate hot flashes. It may not help with other symptoms associated with menopause, such as sleeping difficulties. The findings on St. John’s wort on its own are mixed.

Learn about other Natural Approaches to Menopause.

3) Plaque Psoriasis

Preliminary research suggests that the topical application of St. John’s wort oil or ointment may decrease the size and severity of patches in plaque psoriasis. 

4) Wound Healing

The oil of St. John's wort, applied to skin, was a folk remedy for skin injuries, nerve pain, burns and hemorrhoids.

The oil (or ointment) may be standardized to hypericin or hyperforin, which are thought to have anti-inflammatory and antibacterial effects, and it also contains tannins, compounds thought to help with certain types of skin irritation. Applying a St. John’s wort-based ointment three times a day for 16 days has been found to improve wound healing and reduce scar formation, according to one study.

Read about the possible safety concerns and drug interactions on page 2.


In published studies, the most common side effects associated with short-term oral use of St. John’s wort supplements have included mild stomach upset, allergic skin reactions, tiredness, restlessness, anxiety, sexual or erectile dysfunction, dizziness, photosensitivity, vivid dreams, diarrhea, tingling, dry mouth and headache. Side effects associated with topical use include skin rash.

St. John’s wort (both oral or topical) increases the sensitivity of skin and eyes to sunlight.

Sun exposure may cause severe skin reactions. People who do take St. John's wort should always wear sun block and take other precautions, regardless of the time of day or year or their skin tone.

Pregnant should not use St. John's wort. Side effects (such as colic, drowsiness) have been reported in nursing infants, so breastfeeding mothers should avoid St. John's wort. Women who are trying to conceive should avoid St. John's wort.

St. John’s wort has been associated with serotonin syndrome (a potentially dangerous condition resulting from an excess of serotonin in the central nervous system) when taken with antidepressants such as SSRIs. Symptoms may include confusion, fever, hallucinations, nausea, loss of muscle coordination, sweating, and shakiness. If you experience any of these symptoms, stop taking St. John’s wort and seek immediate medical attention.

  • There are some concerns that St. John's wort might worsen symptoms in people with attention deficit-hyperactivity disorder (ADHD), bipolar disorder (it may bring on mania or speed up the cycling), major depression, schizophrenia (may bring on psychosis), and Alzheimer's disease. 
  • People with diagnosed or suspected depression should consult a doctor to ensure that their condition is properly assessed and treated.
  • Pregnant or breastfeeding women, and those trying to conceive, should avoid St. John's wort.
  • St. John’s wort should not be taken by organ transplant recipients, as it may cause organ rejection.
  • St. John's wort should not be taken within two weeks before a scheduled surgery. Some sources caution that use of St. John's wort for six months may lead to heart complications in people undergoing anesthesia with surgery. 
  • In one small study, St. John’s wort was associated with elevated thyroid stimulating hormone (TSH) levels.

Possible Drug Interactions

One of the major downsides of using St. John’s wort is that it may interact in a potentially harmful way with many common drugs and supplements. It's broken down in the liver by enzymes that also process certain medications, the result being potentially decreased effectiveness of other medications or heightened effect, leading to an increased risk of adverse effects.

Here is a list of some of the medications that may interact with St. John's wort. It's crucial to consult your physician before taking St. John's wort or before making any change to your treatment. Do not stop taking prescription drugs without consulting your doctor. Avoiding or delaying standard care and self-treating with alternative medicine may have serious consequences.

  • Antidepressants - St. John's wort may increase the side effects of medications used to treat depression and other disorders, such as tricyclic antidepressants, SSRIs, and monoamine oxidase inhibitors (MAOIs) and it could lead to a dangerous condition called serotonin syndrome. These medications may include paroxetine (Paxil®), sertraline (Zoloft®), fluoxetine (Prozac®), citalopram (Celexa®), fluvoxamine (Luvox®), amitriptyline (Elavil®), clomipramine (Anafranil®), imipramine (Tofranil®), phenelzine, (Nardil®), and others.
  • Allergy drugs - e.g. fexofenadine (Allegra®)
  • Dextromethorphan (DM), an ingredient in many non-prescription cough and cold products (e.g. Robitussin® DM) to relieve cough. Use with St. John's wort may increase serotonin levels, resulting in a greater risk of adverse effects. 
  • Digoxin (Lanoxin®) – St. John’s wort may reduce its effectiveness

  • Drugs that suppress the immune system - e.g. cyclosporine (Neoral®, Sandimmune®), adalimumab (Humira®), azathioprine (Imuran®), etanercept (Enbrel®), methotrexate, mycophenolate mofetil (CellCept®),Tacrolimus (Prograf®), sirolimus (Rapamune®), daclizumab (Zenapak®)

  • Oral contraceptives – St. John’s wort has been known to cause breakthrough bleeding and may decrease the effectiveness of birth control pills.

  • Reserpine – St. John’s wort blocks the effect of this drug.

  • Triptans (used to treat migraines) - e.g. frovatriptan (Frova®), naratriptan (Amerge®), rizatriptan (Maxalt®), sumatriptan (Imitrex®), zolmitriptan (Zomig®)

  • Photosensitizing drugs

  • Antibiotics, such as ciprofloxacin (Cipro®) and tetracycline (Achromycin)
  • Antifungal drugs - e.g. ketoconazole (Nizoral®), itraconazole (Sporanox®), fluconazole (Diflucan®)

  • Sedative drugs - When used together with St. John’s wort, the sedative effect may be exaggerated. e.g. anticonvulsant drugs, barbiturates, benzodiazepines, alcohol, insomnia medication, tricyclic antidepressants.

  • Statin drugs (to lower cholesterol) - e.g. simvastatin (Zocor®), lovastatin (Mevacor®), atorvastatin (Lipitor®)

  • Theophylline - St. John’s wort may reduce the effectiveness of theophylline, a medication used for asthma, emphysema and chronic bronchitis. E.g. Aerolate®, T-Phyl®, and Uniphyl®

  • Warfarin (Coumadin®) – St. John’s wort may reduce the effectiveness of warfarin, increasing the risk of blood clots. St. John’s wort may possibly influence the effectiveness of other anticlotting drugs or similar drugs known as antiplatelet drugs.

  • Certain calcium channel blockers, such as diltiazem (Tiazac®) and nifedipine (Adalat®)

  • Cancer medications, such as irinotecan (Camptosar®), imatinib (Gleevec®), paclitaxel (Taxol®), vinblastine (Velbe®), and vincristine (Oncovin®)

  • Loperamide (Imodium®) – A case report of deliurium developing in an otherwise healthy woman taking St. John’s wort and the antidiarrhea medication loperamide.

  • Nefazodone (Serzone®)

  • Non-nucleoside reverse transcriptase inhibitors, such as delavirdine (Rescriptor®) and nevirapine (Viramune®),

  • Protease inhibitors such as indinavir (Crixivan®), ritonavir (Norvir®), and nelfinavir (Viracept®).

  • Psoralen medications, such as methoxsalen or methoxypsoralen (8-MOP)

  • Verapamil

Possible Supplement Interactions

  • Supplements that increase serotonin - e.g. 5-hydroxytryptophan (5-HTP), L-tryptophan, SAMe, Hawaiian baby woodrose.
  • Iron - St. John's wort may decrease the absorption of iron.
  • Red yeast rice
  • Supplements that contain cardiac glycosides.


Chung DJ, Kim HY, Park KH, et al. Black cohosh and St. John's wort (GYNO-Plus) for climacteric symptoms. Yonsei Med J 2007;48:289-94.

Kim HL, Streltzer J, Goebert D (1999). St. John's wort for Depression: A Meta-Analysis of Well-Defined Clinical Trials. J Ment Nerv Dis 187 (9), 532-538.

Kobak KA, Taylor LV, Bystritsky A, Kohlenberg CJ, Greist JH, Tucker P, Warner G, Futterer R, Vapnik T. St John's wort versus placebo in obsessive-compulsive disorder: results from a double-blind study. Int Clin Psychopharmacol. (2005) 20.6: 299-304.

Najafizadeh, P., Hashemian, F., Mansouri, P., Farshi, S., Surmaghi, M. S., and Chalangari, R. The evaluation of the clinical effect of topical St Johns wort (Hypericum perforatum L.) in plaque type psoriasis vulgaris: a pilot study. Australas.J.Dermatol. 2012;53(2):131-135. 

Randløv C, Mehlsen J, Thomsen CF, Hedman C, von Fircks H, Winther K. The efficacy of St. John's Wort in patients with minor depressive symptoms or dysthymia - a double-blind placebo-controlled study. Phytomedicine. (2006) 13.4: 215–221.

Samadi S, Khadivzadeh T, Emami A, et al. The effect of Hypericum perforatum on the wound healing and scar of cesarean. J Altern Complement Med 2010;16:113-7. 

Uebelhack R, Blohmer JU, Graubaum HJ, et al. Black cohosh and St. John's wort for climacteric complaints: a randomized trial. Obstet Gynecol 2006;107(2 Pt 1):247-55.

Disclaimer: The information contained on this site is intended for educational purposes only and is not a substitute for advice, diagnosis or treatment by a licensed physician. It is not meant to cover all possible precautions, drug interactions, circumstances or adverse effects. You should seek prompt medical care for any health issues and consult your doctor before using alternative medicine or making a change to your regimen.

Continue Reading