In modern medicine, St. John's wort is used increasingly often as a treatment for mild-to-moderate depression since it has fewer side effects than traditional anti-depressants. If there's a little weasely voice inside your brain, constantly telling you you're worthless - taking St. John's wort as an anti-depressant may help you fight off that only-too-real monster. (*)
In fantasy stories, the herb wards off more tangible (if fictional) monsters. Take for example this snippet from Fire Touched by Patricia Briggs, where the main character Mercy Thompson is attacked by a troll:
It was probably coincidence that I remembered the essential oil that Zack had shoved into my pocket as soon as I touched the walking stick. I pulled it out of my pocket and saw at a glance that Zack had gotten it right, grabbed the Rest Well and not any of the other oils that I'd bought. The Rest Well had been mostly St. John's wort. [..]
For lack of any better idea, or any more time to fuss, I swept my hand out from left to right, scattering the liquid in front of me in a rough semicircle. [..]
I narrowed my eyes at the troll and thought, Bring it. The troll, so close that I could feel his breath, stepped on the pavement where I'd dropped the essential oils and staggered back as if he'd hit a wall.
There are quite a few sources confirming the effectiveness of St. John's wort against fairies (or the Fae, as they're called in Brigg's Mercy Thompson series), as well as several others that claim the herb as a defense against other magical creatures, or the blights and illnesses they may cause.
Usually, though, the herb itself is used, either by ingesting it or by putting a living or dried plant onto window sills or hanging it over a door. Mercy in the above snippet is lucky: The herb's magical properties have apparently survived the distillation process that created the essential oil she's using against her otherworldly attacker.
As mentioned above, St. John's wort in modern medicine is best-known for its use as an anti-depressant, though it also has anti-bacterial and anti-inflammatory properties and can be used to treat wounds and burns.
The University of Maryland Medical Center lists the above points as St. John's wort's healing properties, and goes on to state that the herb has also shown promise in treating premenstrual syndrome (PMS), menopause symptoms, and seasonal affective disorder (SAD).
The German Kommission E recommends St. John's wort oil extracts for use against wounds and blunt injuries, and also to treat muscle pains.
And, to conclude with an interesting oddity:
Cochrane found that the herb is an effective antidepressant - but more so in German-speaking countries than in the rest of the world.
I won't even attempt to get the the bottom of that particular mystery - I'll leave it you, my readers, to come up with an explanation. And one day, maybe medical science will solve the riddle for us.
(*) As for all remedies discussed on this blog, the usual disclaimer applies (see below): Do not try this remedy without your physician's approval. For St. John's wort this is especially important, since depression is a serious illness that should never be treated lightly. Also, the herb interacts dangerously with other anti-depressants, and may render birth control pills and other drugs ineffective.
*** Please note: This blog is not intended as medical advice. ***
Do not try this at home.
(Or at least, don't use any of the remedies described here this without consulting your physician first.)