List Of Herbs With Known Adverse Effects

This is a partial list of herbs and herbal treatments with known or suspected adverse effects, either alone or in interaction with other herbs or drugs. Non-inclusion of an herb in this list does not imply that it is free of adverse effects. In general, the safety and effectiveness of alternative medicines have not been scientifically proven and remain largely unknown. Beyond adverse effects from the herb itself, “adulteration, inappropriate formulation, or lack of understanding of plant and drug interactions have led to adverse reactions that are sometimes life threatening or lethal.”

Most of the adverse effects stated in this list are associated with only a small percentage of cases; they should be understood as potential risks rather than as certainties.

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by expanding it with reliably sourced entries.

Herbs, treatments, and constituents with known or suspected adverse effects

Name Other common names Scientific name Adverse effects
Aconite monkshood, wolfsbane, aconitum Aconitum spp. Heart palpitations and arrhythmias, hypotension, nausea, vomiting, abdominal pain, respiratory system paralysis, death
Aloe vera juice medicinal aloe Aloe vera “abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents”
Anthranoid laxatives “abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents”
Areca nut betel nut Areca catechu “deterioration of psychosis in patients with preexisting psychiatric disorders”; known carcinogen contributing to cancer of the mouth, pharynx, esophagus and stomach when chewed.
Aristolochic acid (contained in herbs in the genus Aristolochia), Aristolochia reticulata (Texas snakeroot) and in Chinese herbs such as Aristolochia fangchi and Aristolochia manshuriensis (banned in China and withdrawn from Chinese Pharmacopoea 2005; Stephania tetrandra and Magnolia officinalis do not contain aristolochic acid). Kidney toxicity associated with kidney failure; associated with development of cancer, particularly of the urinary tract, known carcinogen
Atractylate Atractylis gummifera Liver damage, nausea, vomiting, epigastric and abdominal pain, diarrhoea, anxiety, headache and convulsions, often followed by coma
Ayurvedic Herbo-mineral (Rasashastra) Medicines Heavy metal contamination
Bitter orange ‘Fainting, arrhythmia, heart attack, stroke, death’
Broom broom flower, dyer’s broom, dyer’s greenwood, dyer’s weed, dyer’s whin, furze, green broom, greenweed, wood waxen Genista tinctoria Uterotonic properties, nausea vomiting, and diarrhea, contraindicated for pregnancy and breast feeding
Buckthorn bark and berry alder buckthorn Rhamnus frangula “abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents”
Cascara Sagrada bark bearberry Rhamnus purshiana “abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents”
Chaparral creosote bush, gobernadora, larreastat Larrea tridentata, Larrea divaricata Liver damage, kidney problems, Hypotension in cancer patients
Chinese herbal mixtures Heavy metal poisoning
Coltsfoot coughwort, farfarae folium leaf, foalswort Tussilago farfara Liver damage, cancer
Comfrey comphrey, blackwort, common comfrey, slippery root Symphytum officinale Liver damage, cancer
Country mallow heartleaf, silky white mallow Sida cordifolia “Heart attack, heart arrhythmia, stroke, death”
Dan Shen red sage, Chinese sage, tan shen Salvia miltiorrhiza Potentiates warfarin activity, leading to excessive anticoagulation and bleeding
Dong quai female ginseng Angelica sinensis May induce uterine contractions; contraindicated when pregnant or nursing
European Mistletoe common mistletoe Viscum album Toxic to cardio and central nervous systems, gastrointestinal bleeding
Ephedra ma huang Ephedra sinica Agitation and palpitations, “hypertension, irregular heart rate, insomnia, nervousness, tremors and seizures, paranoid psychoses, heart attacks, strokes, and death”, kidney stones
Flavonoids (contained in many medicinal plants) Vitamin P, citrin Flavonoids, bioflavonoids Hemolytic anemia, kidney damage
Germander Teucrium Liver damage
Ginger Zingiber officinale May increase the risk of bleeding
Ginkgo gingko Ginkgo biloba Bleeding
American Ginseng American Ginseng, Canadian Ginseng, Ginseng, Ginseng Root, North American Ginseng, Occidental Ginseng, Ontario Ginseng, Panax quinquefolium, Panax quinquefolius, Red Berry, Ren Shen, Sang, Shang, Shi Yang Seng, Wisconsin Ginseng Panax quinquefolius “Hypertensive and chronotropic activities, may increase digoxin levels”, diarrhea, itching, insomnia, headaches, nervousness, rapid heartbeat, hypertension or hypotension, breast tenderness, vaginal bleeding. Very rarely Stevens–Johnson syndrome, liver damage, severe allergy has been reported May lower blood sugar excessively in combination with diabetes medication. Contains a chemical linked to possible birth defects. May worsen hormone sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, and uterine fibroids. Insomnia.
Goldenseal orangeroot, yellow puccoon Hydrastis canadensis Uterotonic
Greater celandine celandine Chelidonium majus Liver damage
Guarana Paullinia cupana Agitation and insomnia
Guar gum guaran Obstruction of gastrointestinal tract
Gugulipid guggal, guggul, Mukul myrrh tree Commiphora mukul “Headache, nausea, hiccups, diminished efficacy of other cardiovascular drugs including diltiazem and propranolol”
Hawthorn common hawthorn, may, mayblossom, maythorn, quickthorn, whitethorn, motherdie, haw Crataegus monogyna “Potentiates digitalis activity, increases coronary dilation effects of theophylline, caffeine, papaverine, sodium nitrate, adenosine and epinephrine, increase barbiturate-induced sleeping times”
Horse chestnut conker tree, conker Aesculus hippocastanum Liver toxicity, allergic reaction, anaphylaxis
Kava awa, kava-kava Piper methysticum Potentates CNS sedatives, chronic use might cause a reversible dry skin condition.
Khat qat Catha edulis Chronic liver dysfunction
Kratom Mitragyna speciosa Hepatotoxicity
Liquorice root Glycyrrhiza glabra Hypokalemia, hypertension, arrhythmias, edema
Lobelia asthma weed, pukeweed, vomit wort Lobelia inflata Toxicity, rapid heartbeat, hypotension, coma, death
Milk thistle Marian thistle Silybum marianum Mild laxative, allergy
Pennyroyal Mentha pulegium Liver damage
Peony Bai Shao, Chi Shao, Chinese peony, common peony, coral peony, Cortex Moutan, European peony, Jiu Chao Bai Shao, Moutan, Mu Dan PI, peony flower, peony root, piney, radix peony, red peony, Shakuyaku, Shao Yao, tree peony, Ud Saleeb, Udsalam, Udsalap, White Peony Radix Paeoniae, Radix Paeoniae Alba, Radix Paeoniae Rubra, Paeonia, Paeonia alba, Paeonia lactiflora, Paeonia mascula; Paeonia obovata; Paeonia officinalis; Paeonia suffruticosa, Paeonia veitchii, Paeoniae Flos, Paeoniae Radix May slow clotting; contraindicated for people with bleeding disorders and before and after surgery. May induce uterine contractions; contraindicated when pregnant or nursing.
Pyrrolizidine alkaloids (contained in comfrey, borage, senecio, coltsfoot, and others) Liver damage
Reserpine Rauvolfia serpentina “Sedation, inability to complete tasks, mental depression, nasal congestion, increased gastric secretion and mild diarrhea”
Safrole Sassafras albidum Liver damage
Saw palmetto Serenoa repens “rare and mild gastrointestinal upset, headaches, diarrhea, gynecomastia, paroxysmal atrial fibrillation, ventricular rupture and death in one patient”
Senna Egyptian senna Senna alexandrina (Cassia senna) “abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents”, liver damage
St John’s wort Tipton’s weed, Klamath weed Hypericum perforatum Photosensitization, GI disturbances, “allergic reactions, fatigue, dizziness, confusion, dry mouth”
Valerian garden valerian, garden heliotrope, all-heal Valeriana officinalis “drowsiness, GI upset, headache, palpitations, insomnia”, oversedation, overstimulation
Vasambu sweet flag Acorus calamus Vomiting and nausea
Yohimbe yohimbine Pausinystalia johimbe rapid heart rate, hypertension, hypotension, heart problems, death
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Herbal medicine

Herbs with adverse drug interactions

Name Other common names Scientific name Drug Adverse effects
Cinchona bark Cinchona pubescens Warfarin Possibly additive
Chamomile Blood thinners
Devil’s Claw grapple plant, wood spider Harpagophytum Warfarin Additive effects
Ephedra Ephedra Caffeine, decongestants, stimulants
Feverfew featherfew Tanacetum parthenium Aspirin Additive effects
Garlic Allium sativum Warfarin Additive effects
Ginger Zingiber officinale Warfarin Additive effect, causes iris bleeding
Ginkgo gingko Ginkgo biloba Aspirin, warfarin, ticlopidine, clopidogrel, dipyridamole, garlic, vitamin E With aspirin – retards aspirin absorption
Ginseng Panax ginseng Warfarin
Papayaextract Carica papaya Warfarin Damage to GI tract mucous membranes, Possibly additive, purpura
Kava kava-kava Piper methysticum Sedatives, sleeping pills, antipsychotics, alcohol
Milkvetch Astragalus Astragalus may interact with medications that suppress the immune system, such as cyclophosphamide. It may also affect blood sugar levels and blood pressure.
Pineappleenzyme Ananas comosus Bromelain “Diarrhea, increased tendency for bleeding if used simultaneously with anticoagulants and inhibitors of thrombocytic aggregation due to modulation of the arachidonate cascade”
Psylliumseed Plantago spp Coumarin derivates Retards absorption of drug
St John’s wort Tipton’s weed, Klamath weed Hypericum perforatum Antidepressants, warfarin, protease inhibitors for HIV, birth control, some asthma drugs, and many other medications
Orchid Orchid Flower Bamboo Luck Bamboo Relaxation

Orchid Flower Bamboo Relaxation

Herbal plants associated with allergic reactions

  • Angelica
  • Aniseed
  • Apricot
  • Arnica
  • Artichoke
  • Asafoetida
  • Boneset
  • Cassia
  • Celery
  • Cinnamon
  • Cowslip
  • Dandelion
  • Elecampane
  • Euphorbia
  • Feverfew
  • Fucus
  • Gravel root
  • Guaiacum
  • Holy Thistle
  • Hops
  • Hydrangea
  • Hydrocotyle
  • Juniper
  • Lady’s slipper
  • Meadowsweet
  • Milk thistle
  • Motherwort
  • Parsley
  • Pilewort
  • Plantain
  • Pulsatilla
  • Rosemary
  • Tansy
  • Vitex agnus-castus
  • Wild carrot
  • Yarrow

See also

Adapted from Wikipedia, the free encyclopedia