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.
Herbs, treatments, and constituents with known or suspected adverse effects NameOther common namesScientific nameAdverse effectsAconitemonkshood, wolfsbane, aconitumAconitum spp.Heart palpitations and arrhythmias, hypotension, nausea, vomiting, abdominal pain, respiratory system paralysis, deathAloe vera juicemedicinal aloeAloe 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 nutbetel nutAreca 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 e.g. Aristolochia serpentaria (Virginia snakeroot), 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(Texas snakeroot) and in Chinese herbs such as Aristolochia fangchi and Aristolochia manshuriensis (banned in China and withdrawn from Chinese Pharmacopoea 2005; Stephania tetrandra and Magnolia officinalis do not contain aristolochic acid).Kidney toxicity associated with kidney failure;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 carcinogenAtractylateAtractylis gummiferaLiver damage, nausea, vomiting, epigastric and abdominal pain, diarrhoea, anxiety, headache and convulsions, often followed by comaAyurvedic Herbo-mineral (Rasashastra) Medicines Heavy metal contaminationBitter orange'Fainting, arrhythmia, heart attack, stroke, death'Broombroom flower, dyer's broom, dyer's greenwood, dyer's weed, dyer's whin, furze, green broom, greenweed, wood waxenGenista tinctoriaUterotonic properties, nausea vomiting, and diarrhea, contraindicated for pregnancy and breast feedingBuckthorn bark and berryalder buckthornRhamnus frangula"abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents"Cascara sagrada barkbearberryRhamnus purshiana"abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents"Chaparralcreosote bush, gobernadora, larreastatLarrea tridentata, Larrea divaricataLiver damage, kidney problems, Hypotension in cancer patientsChinese herbal mixturesHeavy metal poisoningColtsfootcoughwort, farfarae folium leaf, foalswortTussilago farfaraLiver damage, cancerComfreycomphrey, blackwort, common comfrey, slippery rootSymphytum officinaleLiver damage, cancerCountry mallowheartleaf, silky white mallowSida cordifolia"Heart attack, heart arrhythmia, stroke, death"Dan Shenred sage, Chinese sage, tan shenSalvia miltiorrhizaPotentiates warfarin activity, leading to excessive anticoagulation and bleedingDong quaifemale ginsengAngelica sinensis May induce uterine contractions; contraindicated when pregnant or nursingEuropean Mistletoecommon mistletoeViscum albumToxic to cardio and central nervous systems, gastrointestinal bleedingEphedrama huangEphedra sinicaAgitation and palpitations, "hypertension, irregular heart rate, insomnia, nervousness, tremors and seizures, paranoid psychosis, heart attacks, strokes, and death", kidney stonesFlavonoids (contained in many medicinal plants)Vitamin P, citrinFlavonoids, bioflavonoidsHemolytic anemia, kidney damageGermanderTeucriumLiver damageGingerZingiber officinaleMay increase the risk of bleedingGinkgogingkoGinkgo bilobaBleedingAmerican GinsengAmerican 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.Goldensealorangeroot, yellow puccoonHydrastis canadensisUterotonicGreater celandinecelandineChelidonium majusLiver damageGuaranaPaullinia cupanaAgitation and insomniaGuar gumguaranObstruction of gastrointestinal tractGugulipidguggal, guggul, Mukul myrrh treeCommiphora mukul"Headache, nausea, hiccups, diminished efficacy of other cardiovascular drugs including diltiazem and propranolol"Hawthorncommon hawthorn, may, mayblossom, maythorn, quickthorn, whitethorn, motherdie, hawCrataegus monogyna"Potentiates digitalis activity, increases coronary dilation effects of theophylline, caffeine, papaverine, sodium nitrate, adenosine and epinephrine, increase barbiturate-induced sleeping times"Horse chestnutconker tree, conkerAesculus hippocastanumLiver toxicity, allergic reaction, anaphylaxisKavaawa, kava-kavaPiper methysticumPotentiates CNS sedatives, chronic use might cause a reversible dry skin condition. KhatqatCatha edulisChronic liver dysfunctionKratomMitragyna speciosaHepatotoxicityLiquorice rootGlycyrrhiza glabraHypokalemia, hypertension, arrhythmias, edemaLobeliaasthma weed, pukeweed, vomit wortLobelia inflataToxicity, rapid heartbeat, hypotension, coma, deathMilk thistleMarian thistleSilybum marianumMild laxative, allergyPennyroyalMentha pulegiumLiver damagePeonyBai 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 PeonyRadix 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 RadixMay 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 damageReserpineRauvolfia serpentina"Sedation, inability to complete tasks, mental depression, nasal congestion, increased gastric secretion and mild diarrhea"SafroleSassafras albidumLiver damageSaw palmettoSerenoa repens"rare and mild gastrointestinal upset, headaches, diarrhea, gynecomastia, paroxysmal atrial fibrillation, ventricular rupture and death in one patient"SennaEgyptian sennaSenna alexandrina (Cassia senna)"abdominal pain, diarrhea, potentially carcinogenic, with others can potentiate cardiac glycosides and antiarrhythmic agents", liver damageSt John's wortTipton's weed, Klamath weedHypericum perforatumPhotosensitization, GI disturbances, "allergic reactions, fatigue, dizziness, confusion, dry mouth"Valeriangarden valerian, garden heliotrope, all-healValeriana officinalis"drowsiness, GI upset, headache, palpitations, insomnia", oversedation, overstimulationVasambusweet flagAcorus calamusVomiting and nauseaYohimbeyohimbinePausinystalia johimberapid heart rate, hypertension, hypotension, heart problems, death
Herbs with adverse drug interactions NameOther common namesScientific nameDrugAdverse effectsCinchona barkCinchona pubescensWarfarinPossible additive effectChamomileBlood thinnersDevil's Clawgrapple plant, wood spiderHarpagophytumWarfarinAdditive effectEphedraEphedraCaffeine, decongestants, stimulantsIncreases sympathomimetic effect of ephedraFeverfewfeatherfewTanacetum partheniumAspirinAdditive effectGarlicAllium sativumWarfarinAdditive effectGingerZingiber officinaleWarfarinAdditive effect, causes iris bleedingGinkgogingkoGinkgo bilobaAspirin, warfarin, ticlopidine, clopidogrel, dipyridamole, garlic, vitamin EWith aspirin – retards aspirin absorptionGinsengPanax ginsengWarfarinPapaya extractCarica papayaWarfarinDamage to GI tract mucous membranesKavakava-kava Piper methysticumSedatives, sleeping pills, antipsychotics, alcoholMilkvetchAstragalusAstragalus may interact with medications that suppress the immune system, such as cyclophosphamide. It may also affect blood sugar levels and blood pressure. Pineapple enzymeAnanas comosusBromelain"Diarrhea, increased tendency for bleeding if used simultaneously with anticoagulants and inhibitors of thrombocytic aggregation due to modulation of the arachidonate cascade"Psyllium seedPlantago sppCoumarin derivatesRetards absorption of drugSt John's wortTipton's weed, Klamath weedHypericum perforatumAntidepressants, warfarin, protease inhibitors for HIV, birth control, some asthma drugs, and many other medications
Herbal plants associated with allergic reactions
See also Alternative medicine Herbalism List of branches of alternative medicine List of plants used in herbalism List of poisonous plants
References