Health hazards of unusual herbal teas

Health hazards of unusual herbal teas

Paul M. Ridker

Health Hazards of Unusual Herbal Teas Some unusual herbal teas have potentially serious toxic effects. Because most commercially available herbal products are safe, a high index of suspicion is required to detect subtle cases of herbal tea toxicity. Reported effects include anticoagulation, hepatic veno-occlusive disease, orthostatic hypotension, anticholinergic syndrome and cardiac arrhythmias. The majority of commercially available herbal teas are healthy alternatives to coffee and common caffeinated tea. A few unusual herbal teas, however, can cause gastrointestinal, hepatic, hematologic and nervous system abnormalities. Most physicians and consumers have only limited knowledge of these problems. Primary care physicians should be aware that herbal compounds may cause a wide range of clinical presentations.

Illustrative Cases


A 42-year-old man is seen for recurrent bruising and evaluation of a prolonged prothrombin time. The patient is taking no anticoagulant medications and avoids aspirin and other prostaglandin inhibitors. Suspicious about alcohol consumption, the physician asks the patients about his fluid intake. “Not a drop of alcohol,” the patient replies, “but I do like my herbal [woodruff] tea.”


An 80-year-old woman, disoriented and confused, is seen for a second time in the emergency department. Examination reveals orthostatic hypotension. The patient has had diarrhea, but stool cultures have been negative and there is no blood in the stool. The patient improves with hydration. At discharge, the physician suggests that the patient’s “tea and toast” meals should include more of the former. The patient smiles, since buckthorn tea is one of her favorite drinks.


A 38-year-old woman develops hepatosplenomegaly, edema and ascites, with dramatic weight gain over three months. She has no history of alcohol use, and a hepatitis screen is negative. Her clinical examination and work-up are consistent with Budd-Chiari syndrome, but no evidence of hypercoagulability or obstruction of the vena cava is found. Liver biopsy reveals progressive veno-occlusive disease, and the patient undergoes portacaval bypass surgery.

After the operation, the patient continues to do poorly despite diuretics, lactulose therapy and rigid adherence to a low-protein diet. Her physician then discovers that she is continuing to drink a daily cup of comfrey tea.


Although few 20th-century physicians would correctly diagnose the patients in the illustrative cases, our 19th-century counterparts, who were well versed in plant toxicities, would quickly have discontinued the woodruff, buckthorn and comfrey teas that these patients were drinking. Unfortunately, modern-day physicians and consumers lack traditional knowledge of herbal efficacy, dosing and toxicity. As consumer interest in herbal teas increases, exposure to toxic herbs can also be expected to increase.

Herbal medicines played a major role in the development of medical therapeutics. When Dioscorides published his first materia medica in 78 B.C., several hundred plant species were considered to have medicinal value. Plants containing salicylates, opiates, ergotamines and a variety of alkaloids were cataloged by Galen in second-century Rome. Ultimately, pharmacognosy was established as an independent discipline in 19th-century Europe. Only with the relatively recent rise in physician prescription and centralized drug dispensing has the home herbal and the office pharmacopeia disappeared and traditional knowledge of medicinal herbs diminished.

Herbal Tea Toxicity

Most commercial herbal teas are considered safe, although even common commercial tea brewed from Camellia sinensis has been associated with irritability, tremor, ventricular ectopic activity and hypertension, primarily because of its high caffeine content.(1) Adverse effects of the more unusual herbal teas range from mild gastroenteritis to fulminant hepatic failure.


Naturally occurring anticoagulants are present in many common plants, including sumac, parsnip, honeysuckle, mulberry, juniper and clove. None of these plants contain concern. Other species, however, are known to contain up to 3 percent coumarin by weight and can cause significant hemorrhage in susceptible patients.(2,3) One of these species, the tonka bean (Dipteryx odoratum, Coumarouna oppositofolia), was among the first historically mentioned medical sources of coumarin. Melilot (Melilotus officinalis) and woodruff (Asperula odorata, Galium odoratum) also contain significant quantities of coumarin. Patients with recurrent hemorrhage and those already taking anticoagulant agents should be advised to avoid coumarin-containing herbal teas.


A class of compounds known as pyrrolizidine alkaloids is responsible for hepatic veno-occlusive disease. Pyrrolizidine alkaloid poisonings have been reported in Phoenix,(4) Boston(5) and London,(6) underscoring the wide availability of herbs containing these toxic compounds.

Hepatic veno-occlusive disease, a potentially fatal cause of ascites and hepatic failure, is among the most worrisome complications of herbal tea exposure. The disorder is marked by a progressive portal hypertension and the pathologic findings of hepatic central vein dilatation and fibrosis. More than 8,000 cases of hepatic veno-occlusive disease caused by pyrrolizidine alkaloids have been reported worldwide.(7)

Herbal teas that contain pyrrolizidine alkaloids include groundsel (Senecio vulgaris), gordolobo (Senecio longilobus), mate (Ilex paraguayensis), T’u-San-Chi (Gynura segetum), tansy ragwort (Senecio jacobaea) and comfrey (Symphytum officinale). Preparations made from comfrey are available nationwide in tea, powder and capsule forms. Comfrey should be avoided, because it is a well-documented cause of hepatic veno-occlusive disease.(8)

Potential hepatic carcinogenicity has been reported for comfrey,(9) as well as for sassafras root and bark (Sassafras albidum), primarily because of the safrole content in sassafras.(10)


Varying degrees of gastroenteristis, hematochezia, secretory diarrhea and hypotension have been associated with the consumption of tea prepared from pokeroot (Phytolacca americana), buckthorn (Rhamnus catharticus) and senna (Cassia angustifolia).(11,12) Senna and buckthorn both contain anthraquinones and have long been prescribed in low doses for a desired cathartic effect. Pokeroot tea, brewed in this country during the 19th century as an effective antirheumatic agent, was known to cause a cholera-like diarrhea if abused. Unknowing persons who consume sufficient quantities of these teas may experience severe dehydration.


The cardiac glycosides digitalis, digitoxigenin, oleandrin, oleandroside, nerioside, ouabagenin, thevitin and thevetoxin have all been identified in plants accidentally used in herbal tea preparations. Although usually present as a contaminant, foxglove (Digitalis purpurea), squill (Urginea maritima), lily of the valley (Convallaria majalis), yellow oleander (Thevetia peruviana, T. nereifolia) and common oleander (Nerium oleander) should be avoided in herbal teas.(13,15)

When used in herbal tea, true licorice (Glycyrrhiza glabra), can provoke a syndrome of hypernatremia, hypokalemia and hypertension that closely mimics primary hyperaldosteronism.


Lewis Carroll’s account of Alice’s tea party, during which the participants became “mad as a hatter, dry as a bone,” aptly describes the anticholinergic effects of some herbal teas. Blurred vision, dry mouth, dilated pupils, disorientation and delirium may follow the use of mandrake (Mandragora officinarum), lobelia (Lobelia inflata), burdock (Arctium minus, Arctium lappa), and thorn apple or jimson weed (Datura stramonium) preparations. (16-18) Lobelia tea is sold nationwide as an antismoking agent, presumably because of its ability to dry the mouth and thus make cigarettes unpalatable.

Mormon tea (Ephedra nevadensis) and snakeroot (Rauwolfia serpentina), which contain the adrenergic compounds ephedrine and reserpine, may raise catecholamine levels. Tea prepared from the bark of the yohimbe tree (Corynanthe yohimbe) contains yohimbine, a potent presynaptic alpha-blocking agent.

Kavakava tea (Piper methysticum) contains direct central nervous system stimulants, and nutmeg tea (Myristica fragrans) contains the monoamine oxidase inhibitor myristicin.

Final Comment

Only a high index of suspicion will enable physicians to make the diagnosis of herbal tea toxicity. While the vast majority of commercially available herbal products are believed to be safe, a few tea products are capable of producing significant disease. Comfrey tea should be completely avoided.

Family physicians should be aware that herbal tea intake can affect a patient’s well-being. Many tea poisonings occur in patients who grow or mix their own herbal teas, although infrequent poisonings from commercially available brands continue to occur. Labels warning of potentially dangerous side effects of tea constituents are currently not required, and inadvertent exposure to toxic ingredients in herbal teas is likely to continue.(19)

Most commercial herbal teas remain an excellent alternative to coffee and other caffeinated beverages. Physicians can confidently recommend those preparations containing mint, rose hips, blackberry, raspberry and citrus peel. REFERENCES (1)Spiller GA. Overview of the methylxanthine beverages and foods and their effect on health. Prog Clin Biol Res 1984;158:1-7. (2)Thomson WA. Herbs that heal. New York: Scribner, 1976. (3)Hogan RP 3d. Hemorrhagic diathesis caused by drinking an herbal tea. JAMA 1983;249:2679-80. (4)Stillman AS, Huxtable R, Consroe P, Kohnen P, Smith S. Hepatic veno-occlusive disease due to pyrrolizidine (Senecio) poisoning in Arizona. Gastroenterology 1977;73:349-52. (5)Ridker PM, Ohkuma S, McDermott WV, Trey C, Huxtable RJ. Hepatic venocclusive disease associated with the consumption of pyrrolizidine-containing dietary supplements. Gastroenteroloy 1985;88:1050-4. (6)Weston CF, Cooper BT, Davies JD, Levine DF. Veno-occlusive disease of the liver secondary to ingestion of comfrey. Br Med J [Clin Res] 1987;295(6591):183. (7)Huxtable RJ. Herbal teas and toxins: novel aspects of pyrrolizidine poisoning in the United States. Perspect Biol Med 1980;24:1-14. (8)Awang DV. Herbal medicine: comfrey. Can Pharm J 1987;120:100-4. (9)Hirono I, Mori H, Haga M. Carcinogenic activity of Symphytum officinale. JNatl Cancer Inst 1978;61:865-9. (10)Segelman AB, Segelman FP, Karliner J, Sofia RD. Sassafras and herb tea. Potential health hazards. JAMA 1976;236:477. (11)Lewis WH, Smith PR. Poke root herbal tea poisoning [Letter]. JAMA 1979;242:2759-60. (12)Diarrhea from herbal tea–New York, Pennsylvania. MMWR 1978;27:248-9. (14)Bain RJ. Accidental digitalis poisoning due to drinking herbal tea. Br Med J [Clin Res] 1985;290(6482):1624. (15)Haynes BE, Bessen HA, Wightman WD. Oleander tea: herbal draught of death. Ann Emerg Med 1985;14:350-3. (16)Siegel RK. Herbal intoxication. Psychoactive effects from herbal cigarettes, tea, and capsules. JAMA 1976;236:473-6. (17)Bryson PD, Watanabe AS, Rumack BH, Murphy RC. Burdock root tea poisoning. Case report involving a commercial preparation. JAMA 1978;239:2157. (18)Rhoads PM, Tong TG, Banner W Jr, Anderson R. Anticholinergic poisonings associated with commercial burdock root tea. J Toxicol Clin Toxicol 1984-85;22:581-4. (19)Ridker PM. Toxic effects of herbal teas. Arch Environ Health 1987;42:133-6.

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