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St. John's Wort

Botanical name(s):

Hypericum Perforatum. Family: Hypericaceae

Other name(s):

amber, goatweed, hardhay, hyperici herba, klamath weed, tipton weed

General description

St. John's wort is an herb. It has a yellow flower with 5 petals. It grows in much of the world. It’s named after St. John the Baptist. This is because it blooms around his celebration day (June 24). The medicinal part of the plant is made up of the dried above-ground parts. These include the stem, petals, and flowers.

There are 2 chemicals that play a major role in how it works. These are hypericin and hyperforin. These and other related compounds are the main active parts. They may affect serotonin, dopamine, and norepinephrine. These are neurotransmitters in your body. 

Medically valid uses

St. John's wort is used to treat mild to moderate depression. But St. John's wort doesn’t work to treat major or severe depression. 

You can apply oily hypericum forms directly to your skin. It can help treat injuries, muscle pain, and first-degree burns.

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

St. John's wort may have these benefits:

  • Muscle relaxant. It’s used to ease menstrual cramps.

  • Mild tranquilizer. It may calm mood.

  • Nerve tonic. It may have a positive effect on the nervous system.

  • Anti-inflammatory. It may reduce swelling.

  • Astringent. This action contracts tissues or canals of the body.

  • Vulnerary. This may heal wounds and swelling.

  • Antineoplastic. This means it may fight cancer.

  • Antiviral. It may help fight viral infections. These can include herpes and human immunodeficiency virus (HIV).

St. John's wort may be used for nerve pain (neuralgia), anxiety, and tension. It may also aid in weakness, stress, irritability, and sleeping issues (insomnia). It’s also claimed to ease the pain due to some conditions. These include sciatica, rheumatoid arthritis, and menstruation. It may also ease the itching and burning of hemorrhoids and vaginitis.

When you apply it topically, St. John's wort may speed healing in certain conditions. These include bruises, wounds, varicose veins, mild burns, and sunburns.

Dosing format

St. John's wort comes in many forms. These include oil, dried herb, tea, and salve.

It may take 4 to 6 weeks for St. John’s wort to work. If it doesn’t work after this amount of time, you should consider other treatments.

Side effects, toxicity, and interactions

St. John's wort can change the effects of other medicines and can cause serious side effects. These medicines include, but are not limited to:

  • Medicines that prevent organ rejection after an organ transplant. You shouldn’t use St. John’s wort if you’ve had or plan to have an organ transplant.

  • Birth control pills

  • Digoxin

  • Seizure medicines

  • Blood thinners

  • HIV medicines

  • Antidepressants

  • Cancer chemotherapy medicines

St. John’s wort can keep your body from absorbing iron and other minerals.

In large amounts, St. John's wort can make you more sensitive to the sun. This is more a risk for people with fair skin. Stay out of the sun as much as you can. When you must be in the sun, wear sunscreen.

Don’t take large amounts of St. John's wort. Follow the directions on the package.

You shouldn’t take St. John's wort if you have major depression. You also shouldn’t take it if you’re taking a medicine to treat depression.  

Women who are pregnant or breastfeeding should talk to their healthcare providers before taking any supplements.

Online Medical Reviewer: Cynthia Godsey
Online Medical Reviewer: Diane Horowitz MD
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 3/1/2019