Skip to Content
This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER.
NOTE: The information in this summary is no longer being updated and is provided for reference purposes only.
This cancer information summary provides an overview of the use of Essiac and Flor Essence, which are proprietary herbal tea mixtures, as treatments for people with cancer. The summary includes a brief history of the development of Essiac and Flor Essence; a review of laboratory, animal, and human studies; and possible side effects associated with Essiac and Flor Essence use.
This summary contains the following key information:
Many of the medical and scientific terms used in the summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window.
Reference citations in some PDQ cancer information summaries may include links to external websites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of the websites, or of any treatment or product, by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board or the National Cancer Institute.
Essiac and Flor Essence are proprietary herbal tea mixtures produced by different manufacturers. Essiac is reported to contain four herbs: burdock root (Arctium lappa L.), Indian rhubarb root (Rheum palmatum L., sometimes known as Turkish rhubarb), sheep sorrel (Rumex acetosella L.), and the inner bark of slippery elm (Ulmus fulva Michx. [synonym Ulmus rubra]).[1,2,3,4,5,6,7,8,9] Flor Essence is reported to contain the same four herbs as Essiac, plus four potentiating herbs: watercress (Nasturtium officinale R.Br.), blessed thistle (Cnicus benedictus L.), red clover (Trifolium pratense L.), and kelp (Laminaria digitata [Hudson] Lamx.).[2,3,4,10]
The manufacturers of Essiac and Flor Essence both claim they market the original herbal mixture promoted by the developer.[1,10] Although only one company manufactures Flor Essence, several companies produce and market Essiac-like products.[2,3,9] This summary contains information about the trademarked mixtures only and differentiates between the two products wherever possible. Essiac and Flor Essence may vary in their mixture content and effects.
Essiac and Flor Essence are said to detoxify the body and strengthen the immune system.[1,4,6,8,10] Proponents of Essiac further claim that it helps relieve pain, reduce side effects, improves overall quality of life, may reduce tumor size, and may prolong the survival of patients with various types of cancer. The individual herbs in the Essiac and Flor Essence formulas have been shown to contain molecules that have anticancer, anti-inflammatory, antioxidant, or immunostimulatory activity (refer to the Laboratory/Animal/Preclinical Studies section of this summary for more information).[2,3,4,8,12,13,14,15] It is said that the benefits of Essiac and Flor Essence are dependent on the presence of the constituent herbs in the correct proportions. In 2004, a mixture of the Essiac herbs showed a decreased proliferation of a prostate cancer cell line. (Refer to the Laboratory/Animal/Preclinical Studies section of this summary for more information.)
Although the use of Essiac and Flor Essence is generally associated with cancer treatment, both products have been used to treat other health conditions. Essiac has reportedly been used to control diabetes and to treat acquired immunodeficiency syndrome. Flor Essence has reportedly been studied in Russia as a treatment for chronic gastrointestinal diseases (e.g., esophagitis, gastritis, duodenitis, and colitis) and as a treatment for cirrhosis of the liver. However, no controlled data have been published in the peer-reviewed scientific literature to show the safety or the efficacy of Essiac or Flor Essence in patients with cancer or in patients with other health conditions (refer to the Human/Clinical Studies section of this summary for more information).
Essiac and Flor Essence are sold worldwide as health tonics or herbal dietary supplements.[1,10,2,3,4,9] In the United States, health tonics and dietary supplements are regulated as foods, not drugs. Therefore, premarket evaluation and approval by the U.S. Food and Drug Administration (FDA) are not required, and specific disease treatment or prevention claims are not allowed. Because health tonics and dietary supplements are not formally inspected for manufacturing consistency, there may be considerable variation from lot to lot, and there is no guarantee that ingredients identified on product labels are present at all or are present in the specified amounts. The FDA has not approved the use of either Essiac or Flor Essence for the treatment of patients with cancer or any other medical condition.
To conduct clinical drug research in the United States, researchers must file an Investigational New Drug (IND) application with the FDA. An IND application must also be made for clinical evaluation of dietary supplements as agents for the treatment or prevention of disease. The FDA's IND process is confidential, and the existence of an IND application can be disclosed only by the applicants. To date, no investigator has announced filing an IND application to study either Essiac or Flor Essence in the treatment of patients with cancer.
Essiac and Flor Essence are administered orally in the form of herbal teas.[1,4,6,7,8,10,17] Originally, an extract of one of the herbs (not specified) was administered to cancer patients by intramuscular injection at or near tumor sites, and the other herbs were administered orally as a tea.
Only minimal information about dose and schedule of administration is freely available from the manufacturer of Essiac. According to the manufacturer, the dose will vary, depending on the reason for ingestion; the manufacturer's recommended schedules of administration assume a 12-week program of uninterrupted use. Although Essiac is said to be safe for pets, no information is given about its safety in children.
The manufacturer of Flor Essence states that adults may consume from 30 to 360 mL (i.e., 1–12 fl oz) of Flor Essence tea per day, depending on individual requirements, and that it may be used continuously. The manufacturer also suggests that Flor Essence may be safely consumed by infants and children, but its use by pregnant women and nursing mothers is not recommended. However, the promotion of mammary tumors observed in a rat model of breast cancer raises the theoretical concern that Flor Essence may impact normal mammary ductal development during childhood, thereby raising concern about its use.
The manufacturers of Essiac and Flor Essence both state these products can be used in conjunction with other cancer treatments.[1,10] Nonetheless, some proponents of Essiac have recommended that no additional anticancer therapy (such as chemotherapy or radiation therapy) be undertaken while patients are being treated with the mixture. The purported rationale for this statement is that conventional anticancer treatments may alter immune system function and prevent Essiac from working effectively. As indicated previously, no evidence has been reported in the peer-reviewed scientific literature to show either that Essiac is an effective treatment for patients with cancer or that conventional anticancer treatments interfere with its effects.
Essiac was popularized in Canada during the 1920s, when the developer, a nurse from Ontario, began to advocate its use as a cancer treatment. In 1922, the developer obtained an herbal tea formula from a female breast cancer patient who claimed the mixture had cured her disease.[1,2,3,4,5] The patient reportedly received the formula from an Ontario Ojibwa Native American medicine man. The developer subsequently modified the formula, producing both injectable and oral forms of treatment.[2,3,4,5,6,7,8]
From 1934 to 1942, the developer operated a cancer clinic in Bracebridge, Ontario, and dispensed Essiac free of charge. In 1938, members of the Royal Cancer Commission of Canada visited the clinic and heard testimonials from patients who had been treated with the mixture. The Cancer Commission concluded there was only limited evidence for the effectiveness of Essiac. After years of controversy, the developer closed the clinic in 1942 but continued to provide Essiac to patients until the late 1970s. (Refer to the Human/Clinical Studies section of this summary for more information.)
From 1959 until the late 1970s, the developer collaborated with an American physician to conduct clinical and laboratory studies of Essiac and to promote its use. This collaboration led to the development of the eight-herb formula now marketed as Flor Essence. None of the results of these collaborative studies were reported in peer-reviewed scientific journals.
In 1977, the developer provided a four-herb recipe for Essiac to a Canadian corporation.[5,7] In 1978, the corporation filed a preclinical new drug submission with the Canadian Department of National Health and Welfare (Health Protection Branch) and received permission to conduct clinical studies of Essiac's safety and effectiveness in cancer patients.[4,5,7,8] In 1982, this permission was withdrawn when it was determined that the corporation had not fulfilled commitments to adequately control the manufacturing consistency of Essiac, to isolate and characterize active substances in the mixture, and to design and execute appropriate clinical trials.[4,5] During this period, restrictions were imposed on the promotion of Essiac as a cancer treatment, but the corporation was allowed to distribute it to cancer patients through their physicians under Canada's Emergency Drug Release Program (also called Health Canada's Special Access Programme). While the preclinical new drug submission was in effect in Canada, the corporation filed an unsuccessful New Drug Application (NDA) with the U.S. Food and Drug Administration, seeking permission to market Essiac in the United States. Details of the NDA submission, which can be disclosed only by the corporation, have not been made public. (Refer to the Human/Clinical Studies section of this summary for more information.)
In the early 1980s, the Canadian Department of National Health and Welfare (Bureau of Human Prescription Drugs) conducted a retrospective review of case summaries submitted by physicians whose patients had obtained Essiac under the Emergency Drug Release Program.[2,4,7] The Department found little evidence to suggest that Essiac was effective as a cancer treatment. (Refer to the Human/Clinical Studies section of this summary for more information.)
Also in the 1980s, the manufacturers of Essiac-like products began to market their formulations as health tonics and to avoid making claims of effectiveness in treating disease. Consequently, the mixtures were no longer subject to regulation as drugs. Essiac is not currently available under Canada's Emergency Drug Release Program.
In 1995, the corporation that acquired the four-herb recipe for Essiac from the developer dissolved voluntarily. Later that year, a new company was formed to manufacture and distribute this proprietary herbal mixture.[1,5]
In 2004, a mixture of the Essiac herbs showed a decreased proliferation in a prostate cancer cell line. Results of laboratory (in vitro) studies of Essiac have been reported.[2,3]
In the mid-1970s, the developer submitted both dried and liquid samples of Essiac to the Memorial Sloan Kettering Cancer Center (MSKCC) in New York City for evaluation of its immunotherapeutic and chemotherapeutic potential. No immunostimulatory or chemotherapeutic activity was detected in eight animal experiments that utilized the S-180 mouse sarcoma tumor model.
In the early 1980s, the corporation that acquired the four-herb recipe for Essiac from the developer submitted another sample to the MSKCC for evaluation in additional animal studies. No anticancer activity was detected in 17 separate experiments that utilized a variety of animal leukemia and tumor models.
In 1983, the National Cancer Institute tested a liquid sample of Essiac that was provided by the manufacturer after the Canadian Department of National Health and Welfare (Health Protection Branch) requested that it be tested in animals. These studies revealed no anticancer activity in the mouse P388 lymphocytic leukemia tumor system and found lethal toxicity at the highest concentrations of Essiac administered to test animals. It is not known, however, how the concentrations used in these animal tests compare with the concentrations achieved in humans after the consumption of the manufacturer's recommended doses.
There are conflicting results in the peer-reviewed literature. One study suggests that Flor Essence enhances tumor growth in vitro, a finding that contradicts the widely available anecdotal evidence that this product suppresses or inhibits tumor development. Another study suggests that the growth of human breast cancer cells is stimulated through estrogen receptor (ER)–mediated as well as ER-independent mechanisms of action from Flor Essence and Essiac herbal tonics. A third study demonstrated antiproliferative and differentiation-inducing properties in vitro only in high concentrations of Essiac and Flor Essence herbal teas.
The 2004 in vivo study of Flor Essence in a rat model looked at mammary tumor development following administration of the herbal compound. Sprague-Dawley rats (N = 112) were assigned to one of three groups. The control group (n = 35) received water only. The second group (n = 40) received 3% Flor Essence in their drinking water in an attempt to provide a dose equivalent to that recommended in the popular literature. The third group (n = 37) received 6% Flor Essence in their drinking water to investigate the dose-response relationship. Mammary tumors were induced by a 40 mg/kg of body weight dose of 7,12-dimethylbenz(a)anthracene. At 19 weeks, palpable mammary tumor incidence was higher (65% and 59.4%) in both Flor Essence groups, compared with controls (51%). Terminal necropsy was performed at age 23 weeks or when tumor burden became too great. Results showed mammary tumor incidence was 82.5% for controls, compared with 90% and 97.3%, respectively, for rats consuming 3% and 6% Flor Essence.
The Individual Herbs of Essiac and Flor Essence
Laboratory and animal experiments have shown that some of the chemicals in the herbs used to make Essiac and Flor Essence have antioxidant, anti-inflammatory, estrogenic, or anticancer activity.[7,8,9,10,11,12,13,14,15]
Among the herbs used in both mixtures, burdock root (Arctium lappa L.) contains several flavonoids and polyphenols that have shown antioxidant activity; Indian rhubarb root (Rheum palmatum L.) contains several anthraquinones, including emodin and aloe-emodin, which have demonstrated anti-inflammatory and cytotoxic effects; sheep sorrel (Rumex acetosella L.) contains several types of anthraquinones, including emodin and aloe-emodin, as well as phytoestrogens, which may possess both procancer and anticancer activity; and slippery elm bark (Ulmus fulva Michx.) has been shown to contain antioxidants.[7,8,9,10,11,12,13]
Among the herbs found in Flor Essence alone, watercress (Nasturtium officinale R.Br.) contains phenethyl isothiocyanate (PEITC), which has shown cytotoxic and antitumor activities; blessed thistle (Cnicus benedictus L.) contains cnicin, which is a sesquiterpene lactone that has demonstrated cytotoxic, antitumor, and anti-inflammatory effects, and arctiin and arctigenin, which are lignans that have shown anticancer activity; red clover (Trifolium pratense L.) contains a complex mixture of phytoestrogens, including genistein, which has demonstrated antiangiogenic, estrogenic, and procancer and anticancer effects (depending on the dose); and extracts of kelp (Laminaria digitata [Hudson] Lamx.) have shown immunostimulatory and antitumor activities.[7,8,11,12,15]
Whether equivalent concentrations of relevant molecules can be achieved in the bloodstream of individuals who consume Essiac or Flor Essence in the amounts recommended by their manufacturers has not been determined. An uncharacterized Flor Essence commercial product was dosed at amounts lower than those recommended by the manufacturers for humans, and there was an increase in tumor incidence in this model.
No report of a clinical study of Essiac has been published in the peer-reviewed scientific literature. Brief descriptions of one incomplete clinical study and one retrospective evaluation of Essiac as a treatment for cancer have been published.[1,2,3,4,5,6] It is not clear whether the described patient populations consisted entirely of adults or whether they included children.
As noted previously (refer to the History section of this summary for more information), the developer provided a four-herb recipe for Essiac to a Canadian corporation in 1977.[2,6] In 1978, the corporation filed a preclinical new drug submission with the Canadian Department of National Health and Welfare (Health Protection Branch) and received permission to conduct studies on the safety and the efficacy of Essiac in cancer patients.[2,4,5,6,7] In 1982, the Department withdrew its permission after determining the research was not being conducted as planned (refer to the History section of this summary for more information). At that time, the available incomplete data were reviewed, and no clear evidence of improved survival could be demonstrated for treated patients.[1,2,5,6] Pain control and quality of life were not assessed in these studies. The review of the data indicated, however, that Essiac was not toxic. Because no evidence of harm was found, the Canadian government allowed the corporation to distribute Essiac to cancer patients through their physicians under Canada's Emergency Drug Release Program. Nonetheless, restrictions were imposed on the promotion of Essiac as a treatment for cancer. Access to Essiac under Canada's Emergency Drug Release Program has since been discontinued.
In the early 1980s, the Canadian Department of National Health and Welfare (Bureau of Human Prescription Drugs) conducted a retrospective review of data voluntarily submitted by physicians for 86 cancer patients who had obtained Essiac under Canada's Emergency Drug Release Program between 1978 and 1982.[1,2,4] (Note:  states that data from 87 patients were reviewed.) The Bureau's evaluation was based on written summaries submitted by the physicians and not on a review of the original patient records. The Bureau found 47 patients who did not benefit from Essiac; 1 had subjective improvement, 5 required fewer analgesics, 4 had an objective response, and four were in stable condition.[1,4] Among the remaining 25 patients, 17 had died, and the reports for 8 were considered unevaluable. The Bureau solicited additional information about the four patients who had an objective response and the four patients who were in stable condition. This additional information revealed that, among these eight patients, two had died, three had progressive disease, and three remained in stable condition.[1,4] The three patients in stable condition had received previous conventional therapy. Therefore, the benefits of treatment for these patients, if any, could not be clearly ascribed to Essiac.
No results of human studies of Flor Essence have been reported anecdotally or in the peer-reviewed scientific literature.
Nausea and vomiting are the only reported adverse effects associated with the use of Essiac. The manufacturer of Flor Essence states that users may experience increased bowel movements, frequent urination, swollen glands, skin blemishes, flu-like symptoms, or slight headaches.
To assist readers in evaluating the results of human/clinical studies of integrative, alternative, and complementary therapies for cancer, a scoring system has been devised that allows studies of individual treatments to be ranked according to the strength of their evidence (i.e., their level of evidence). Not all studies, however, are given a level of evidence score. To be eligible, a study must:
Evidence from studies that do not meet these requirements is considered extremely weak. In addition to scoring individual studies, an overall level of evidence assessment is usually made.
Because no study of the use of Essiac or Flor Essence in humans has been reported in a peer-reviewed scientific journal, no level-of-evidence analysis is possible for these mixtures. The data that are available, however, do not support claims that Essiac and Flor Essence can detoxify the body, strengthen the immune system, or fight cancer. At this time, evidence does not support the use of either Essiac or Flor Essence in the treatment of cancer patients outside the context of well-designed clinical trials.
Separate levels-of-evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. For additional information about levels-of-evidence analysis, refer to Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Editorial changes were made to this summary.
This summary is written and maintained by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ® - NCI's Comprehensive Cancer Database pages.
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of Essiac/Flor Essence in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
Board members review recently published articles each month to determine whether an article should:
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewers for Essiac/Flor Essence are:
Any comments or questions about the summary content should be submitted to Cancer.gov through the NCI website's Email Us. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.
Levels of Evidence
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Integrative, Alternative, and Complementary Therapies Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
Permission to Use This Summary
PDQ is a registered trademark. Although the content of PDQ documents can be used freely as text, it cannot be identified as an NCI PDQ cancer information summary unless it is presented in its entirety and is regularly updated. However, an author would be permitted to write a sentence such as "NCI's PDQ cancer information summary about breast cancer prevention states the risks succinctly: [include excerpt from the summary]."
The preferred citation for this PDQ summary is:
PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board. PDQ Essiac/Flor Essence. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: http://www.cancer.gov/about-cancer/treatment/cam/hp/essiac-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389495]
Images in this summary are used with permission of the author(s), artist, and/or publisher for use within the PDQ summaries only. Permission to use images outside the context of PDQ information must be obtained from the owner(s) and cannot be granted by the National Cancer Institute. Information about using the illustrations in this summary, along with many other cancer-related images, is available in Visuals Online, a collection of over 2,000 scientific images.
The information in these summaries should not be used as a basis for insurance reimbursement determinations. More information on insurance coverage is available on Cancer.gov on the Managing Cancer Care page.
More information about contacting us or receiving help with the Cancer.gov website can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the website's Email Us.
Last Revised: 2016-04-11
Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
© Copyright 2017 Rush Copley Medical Center • 2000 Ogden Avenue; Aurora, IL 60504
Main: 630-978-6200 • Physician Referral & Information: 630-978-6700 or 866-4COPLEY (866-426-7539)