P

Polygonum multiflorum dried roots

Claimed to be a cure for baldness and grey hair, as well as being promoted as a immune system booster (though he shou wu contains emodin, a possibly immunosuppresant substance).<wiki/List_of_medicinal_plants#cite_note-hsu-225"> There's not enough evidence to evaluate claims.<wiki/List_of_medicinal_plants#cite_note-hsu-225">

Used for: edema, jaundice, asthma, coughs, menstrual problems, conjunctivitis and blepharitis.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"> It is sometimes used for home abortions, but its effectiveness for this has not been scientifically studied.

The claims: Parsley is touted as a general anti-toxin,<wiki/List_of_medicinal_plants#cite_note-171"> control blood pressure, cure diabetes,<wiki/List_of_medicinal_plants#cite_note-172"> urinary tract infections, prevents cancer, stimulates contractions of the uterus, cures rheumatism, treats kidney and bladder stones,<wiki/List_of_medicinal_plants#cite_note-173"> and can even remove tooth aches.

The truth: Surprisingly, it is dangerous for women, as it can cause the uterus to contract prematurely and should not be inserted into or rubbed near the uterus. It is mildly anti-microbialial — on those days when you can't run to your medicine cabinet and grab a tube of far more effective antibiotic.
Harmful effects: It is harmless when taken in the small amounts found in food, but the large amounts used in herbal medicine may cause anemia and liver or kidney problems, and make water retention, high blood pressure, and kidney disease worse.<wiki/List_of_medicinal_plants#cite_note-parsley-174"> Topically applied parsley oil can make skin become more sensitive to sunlight and cause a rash.<wiki/List_of_medicinal_plants#cite_note-parsley-174">

In TCM: yīngsù (罌粟)<wiki/List_of_medicinal_plants#cite_note-read-12">
Latex exuded by immature seed pod used for analgesic purposes. Tinctures of seeds and straw used to a lesser extent. The latex at least is suggested by research to be effective, albeit prone to habituation and dependency. See also heroin.

Asian ginseng (Panax ginseng); in TCM: rénshēn (人參)<wiki/List_of_medicinal_plants#cite_note-read-12">

American ginseng (P. quinquefolius) is believed by herbalists to have the same constituents as P. ginseng but to be less efficacious than P. ginseng.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7">
Claimed to: be a wonder plant and cure everything.<wiki/List_of_medicinal_plants#cite_note-stuart-5"><wiki/List_of_medicinal_plants#cite_note-theherbbook-7">
Beneficial effects: Ginseng is effective for erectile dysfunction and chronic obstructive pulmonary disease symptoms.<wiki/List_of_medicinal_plants#cite_note-ginseng-19"> A specific cream containing ginseng can help with premature ejaculation.<wiki/List_of_medicinal_plants#cite_note-ginseng-19"> When used with ginkgo leaf extract (see Ginkgo below), ginseng may "improve memory in otherwise healthy people between the ages of and ," but not in young adults.<wiki/List_of_medicinal_plants#cite_note-ginseng-19">
Harmful effects:

Side effects may include insomnia, or, more rarely, menstrual problems, breast pain, increased heart rate, high or low blood pressure, headache, loss of appetite, diarrhea, itching, rash, dizziness, mood changes, vaginal bleeding, Stevens-Johnson syndrome (a severe rash), liver damage, severe allergic reactions<wiki/List_of_medicinal_plants#cite_note-ginseng-19">, mania and psychosis<wiki/List_of_medicinal_plants#cite_note-maniapsychosis-20">.
Panax ginseng contains a substance that has been found to cause birth defects in animals.<wiki/List_of_medicinal_plants#cite_note-ginseng-19">

Effective for anxiety.<wiki/List_of_medicinal_plants#cite_note-kava-139">
Side effects may include liver damage leading to death, even with short-term use (- months) of normal doses,<wiki/List_of_medicinal_plants#cite_note-kava-139"> and sedation, oral and lingual dyskinesia, torticollis, oculogyric crisis, exacerbation of Parkinson's disease, painful twisting movements of the trunk, and rash.<wiki/List_of_medicinal_plants#cite_note-aafp-90"> Several European countries banned or restricted the use of kava based on its hepatotoxic effects; the US FDA only issued a warning.<wiki/List_of_medicinal_plants#cite_note-dietz-140"> A cancer study of kava extract in mice and rats found that it caused liver cancer in male and female mice and "increased incidences of lesions in the liver, forestomach, kidney, eye, and pancreas of male and female rats, in the liver of male and female mice, and in the forestomach of female mice."<wiki/List_of_medicinal_plants#cite_note-141">