H

Hypericum perforatum

See the main article on this topic: St. John's wort

Used for: calming, bedwetting, insomnia, "nervous conditions", depression, anemia, headache, jaundice, congestion, and menstrual difficulties<wiki/List_of_medicinal_plants#cite_note-theherbbook-7">
Regarded by herbalists and some medical authorities as an effective treatment for depression; trials are mixed, partly due to depression's high susceptibility to the placebo effect.<wiki/List_of_medicinal_plants#cite_note-204"><wiki/List_of_medicinal_plants#cite_note-205"> Popular in Germany. May interfere with effectiveness of other drugs.<wiki/List_of_medicinal_plants#cite_note-206">
Harmful effects: may cause cataracts in people exposed to visible or ultraviolet light after taking it.<wiki/List_of_medicinal_plants#cite_note-fordham-207"> Other side effects may include gastrointestinal disturbances, allergic reactions, fatigue, dizziness, confusion, dry mouth, photosensitivity<wiki/List_of_medicinal_plants#cite_note-aafp-90">, mania and psychosis<wiki/List_of_medicinal_plants#cite_note-maniapsychosis-20">

Used for: pain, nervousness, irritability, Parkinson's disease symptoms, and ulcers.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"><wiki/List_of_medicinal_plants#cite_note-hen-123"> It is also smoked to "cure" asthma and bronchitis<wiki/List_of_medicinal_plants#cite_note-hen-123"> (sounds familiar). There is no evidence to support its use for any of these conditions.<wiki/List_of_medicinal_plants#cite_note-henmd-124">
Harmful effects: Henbane is toxic, and when used for self-treatment may result in fatal poisoning. Side effects may include dry mouth, red skin, constipation, overheating, reduced sweating, vision disturbances, increased heart rate, urination problems, drowsiness, restlessness, hallucinations, delirium, manic episodes, and death. Mostly death.
For a while, henbane berries were used in the manufacture of an herbal beer flavoring called "gruit", which was flavored with various sweet and bitter herbs, before people began using hops. Gruit fell out of favor during the Middle Ages when the Reinheitsgebot declared that all beers in the Holy Roman Empire could only be made with barely (Hordeum vulgare), hops (Humulus lupulus), water, and yeast.<wiki/List_of_medicinal_plants#cite_note-Rabin-125">

Used for: vaginal douching, mouthwash, periodontal disease, congestion, laxative, stomach ailments, skin diseases, and nausea relief during pregnancy.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"> Also used for "immune system boosting".<wiki/Help:References" title="Help:References">
Effectiveness: The evidence doesn't suggest Goldenseal is effective for any condition.<wiki/List_of_medicinal_plants#cite_note-110">
Harmful effects: Small doses may be fine, except during pregnancy or breastfeeding, since goldenseal might cause brain damage to the baby.<wiki/List_of_medicinal_plants#cite_note-111">"High doses may cause breathing problems, paralysis, and even death. Long-term use may lead to vitamin B deficiency, hallucinations, and delirium."<wiki/List_of_medicinal_plants#cite_note-gscancer-112">It may also affect blood pressure unpredictably because it contains several different compounds that have opposite effects on blood pressure.<wiki/List_of_medicinal_plants#cite_note-gscancer-112"> It can also make you more sensitive to light.<wiki/List_of_medicinal_plants#cite_note-gscancer-112"> A cancer study of goldenseal root powder in mice and rats showed that it "caused cancer in the liver of male and female rats and male mice. There was no effect of goldenseal root powder on female mice."<wiki/List_of_medicinal_plants#cite_note-113">

Usage: Effective for osteoarthritis pain.<wiki/List_of_medicinal_plants#cite_note-devil-84"> Insufficient study has been done to evaluate its effectiveness for anything else.<wiki/List_of_medicinal_plants#cite_note-devil-84">
Harmful effects: Side effects may include diarrhea, nausea, vomiting, abdominal pain, headaches, ringing in the ears, loss of appetite, and loss of taste.<wiki/List_of_medicinal_plants#cite_note-devil-84"> Other side effects may include allergic skin reactions, menstrual problems, and changes in blood pressure.<wiki/List_of_medicinal_plants#cite_note-devil-84"> Use of devil's claw during pregnancy is not advised, as it may harm the fetus.<wiki/List_of_medicinal_plants#cite_note-devil-84">