Essiac/Flor Essence (PDQ®): Complementary and alternative medicine - Patient Information [NCI]

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Essiac/Flor Essence (PDQ®): Complementary and alternative medicine - Patient Information [NCI]

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 or call 1-800-4-CANCER.

Essiac/Flor Essence


  • Essiac and Flor Essence are herbal tea mixtures that are sold worldwide as health tonics or herbal dietary supplements (see Question 1).
  • Essiac was first promoted as a cancer treatment in the 1920s. Flor Essence was created a number of years later (see Question 2).
  • Supporters of Essiac and Flor Essence say that these products make the immune system stronger, have anti-inflammatory effects, and show anticancer activity (see Question 3).
  • Laboratory, animal, and clinical (human) studies with Essiac and Flor Essence have not reported clear evidence of an anticancer effect (see Question 5 and Question 6).
  • The U.S. Food and Drug Administration has not approved Essiac or Flor Essence as a cancer treatment (see Question 8).

Questions and Answers About Essiac and Flor Essence

What are Essiac and Flor Essence?

Essiac and Flor Essence are herbal tea mixtures that have been used as anticancer treatments. They have been used to treat other health conditions also, including diabetes, AIDS, and gastrointestinal diseases.

Essiac is reported to contain 4 herbs:

  • Burdock root.
  • Indian rhubarb root.
  • Sheep sorrel.
  • Slippery elm (the inner bark).

Flor Essence is reported to contain the same 4 herbs found in Essiac plus these 4 other herbs:

  • Watercress.
  • Blessed thistle.
  • Red clover.
  • Kelp.

Different batches of these mixtures may contain different ingredients or amounts and the effects may not always be the same.

Essiac and Flor Essence are sold worldwide as health tonics or herbal dietary supplements. One company sells Flor Essence and several companies make and sell mixtures called Essiac. This summary refers to the trademarked (brand name) mixtures only.

What is the history of the discovery and use of Essiac and Flor Essence as complementary or alternative treatments for cancer?

A nurse in Canada first began to promote Essiac as a cancer treatment in the 1920s. Today, Essiac and Flor Essence may be sold as herbal supplements as long as they do not claim to treat or cure cancer.

  • In 1922, a breast cancer patient gave the Essiac formula to the nurse and said it had cured her disease. The patient said the formula came from an Ontario Ojibwa Native American medicine man.
  • In 1934, the nurse opened a cancer clinic in Ontario and gave Essiac to patients free of charge. In 1938, the Royal Cancer Commission of Canada visited the clinic but found little evidence that Essiac was effective. The nurse closed the clinic in 1942 but continued to give Essiac to patients until the late 1970s.
  • Between 1959 and the late 1970s, the nurse worked with an American doctor to study Essiac in the laboratory and in people and to promote its use. They also created the formula now called Flor Essence. The results of their studies were not reported in any peer-reviewed scientific journals. Most scientific journals have experts who review research reports before they are published, to make sure that the evidence and conclusions are sound. This is called peer review. Studies published in peer-reviewed scientific journals are considered to be better evidence.
  • In 1977, the nurse gave the formula for Essiac to a company in Canada. In 1978, the government of Canada allowed this company to do clinical studies (research studies with people) on the safety and effectiveness of Essiac. In 1982, it withdrew its permission (see Question 6). This company tried to have Essiac approved as a drug by the US Food and Drug Administration (FDA), but did not get approval.
  • In the 1980s, companies making Essiac-like products began to sell the mixtures as health tonics. Because these companies did not make claims that it would treat or cure certain diseases, Essiac did not come under laws that regulate it as a drug.
What is the theory behind the claim that Essiac and Flor Essence are useful in treating cancer?

Supporters of Essiac and Flor Essence say that when the herbs they contain are mixed in exact amounts, the mixtures make the immune system stronger, have anti-inflammatory effects (decrease swelling, redness, and pain), and show anticancer activity. Individual herbs in the Essiac and Flor Essence formulas have been shown to have these effects, but some of these herbs also have been shown to help cancer grow. No results from controlled trials have been published in peer-reviewed scientific journals on the effect of the exact formulas of Essiac and Flor Essence in patients with cancer or other health conditions. See the PDQ health professional summary on Essiac/Flor Essence for more information on theory.

How are Essiac and Flor Essence administered?

Essiac and Flor Essence are taken orally (by mouth) as herbal teas. According to the companies that make the teas, the proper dose of Essiac depends on why a person is taking it. The maker recommends that Essiac be taken for 12 weeks in a row. The maker of Flor Essence states that adults may take between 30 and 360 milliliters (1 to 12 fluid ounces) of Flor Essence tea a day, depending on individual needs, and may take it on an ongoing basis.

The makers of Essiac and Flor Essence state that the products can be used with other therapies. Some supporters of Essiac, however, recommend that patients avoid any other anticancer therapy (such as chemotherapy or radiation therapy) when taking Essiac, because it may interfere with immune system function and prevent Essiac from working effectively.

Have any preclinical (laboratory or animal) studies been conducted using Essiac or Flor Essence?

Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. Animal tumor models are used to learn how a cancer may progress and to test new treatments. These preclinical studies are done before any testing in humans is begun. The following laboratory and animal studies of Essiac have been reported:

  • In the mid 1970s, the Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City tested dried and liquid samples of Essiac in 8 experiments involving the S–180 mouse sarcoma tumor model (a type of animal model used to study treatment). Researchers found that Essiac did not make the immune system more active and did not act as an anticancer drug.
  • In the early 1980s, researchers at MSKCC tested Essiac again. They found no anticancer activity after doing 17 studies that used a variety of animal leukemia models and other tumor models.
  • In 1983, the National Cancer Institute (NCI) tested a liquid sample of Essiac in the mouse P388 lymphocytic leukemia tumor system but found no anticancer activity. Very high doses of Essiac killed the test animals. Scientists, however, do not know how this finding applies to people who take more than the maker's recommended doses of Essiac.
  • In 2004, a laboratory study at Indiana University-Purdue University reported that Essiac slowed the growth of prostate cancer cells.

Studies of Flor Essence have shown differing results:

  • Two laboratory studies reported that Flor Essence made tumor cells grow.
  • Another laboratory study reported that high doses of both Flor Essence and Essiac herbal teas reduced the growth of cancer cells.
  • A 2004 animal study of Flor Essence found that it increased breast tumor growth in rats.

Laboratory and animal studies have reported on the effects of some of the chemicals found in the different herbs used to make Essiac and Flor Essence. These studies report that certain chemicals may:

  • Prevent cell damage that can lead to cancer.
  • Reduce swelling, redness, and pain.
  • Have an effect on the body similar to the hormone estrogen.
  • Kill cancer cells.

It is not known if taking Essiac and Flor Essence products can give humans enough of the chemicals that produce these effects.

Have any clinical trials (research studies with people) of Essiac or Flor Essence been conducted?

No results of clinical studies (research studies with people) of Flor Essence have been reported. In addition, no reports of clinical trials of Essiac have been reported in peer-reviewed scientific journals. Brief descriptions of one incomplete clinical trial and one review of reports on cancer patients who took Essiac have been published, however.

  • In 1978, the Canadian government gave permission to a Canadian company to begin studying Essiac for safety and effectiveness. In 1982, the government withdrew its permission after it found that the company was not keeping all batches of Essiac exactly the same and was not following the proper rules for clinical trials. A review of data from this incomplete study showed no clear evidence of improved survival in cancer patients who took Essiac. Findings also showed that Essiac was not toxic (harmful).
  • In the early 1980s, the Canadian government reviewed information on 86 cancer patients who had taken Essiac. This was a review of case summaries written by the doctors; the original patient records were not reviewed. The researchers reported that it was not clear if changes in the patients' conditions were caused by Essiac or something else.
Have any side effects or risks been reported from Essiac or Flor Essence?

The only reported side effects caused by Essiac are nausea and vomiting. According to the company making Flor Essence, side effects may include increased bowel movements, frequent urination, swollen glands, skin blemishes, flu-like symptoms, and slight headaches.

Is Essiac or Flor Essence approved by the FDA for use as a cancer treatment in the United States?

The U.S. Food and Drug Administration (FDA) has not approved Essiac or Flor Essence to treat cancer or any other medical condition.

Companies sell Essiac and Flor Essence as health tonics or herbal dietary supplements, which the FDA regulates as foods, not drugs. Essiac or Flor Essence would have to be approved by the FDA as a drug for companies to claim that the products treat or prevent a disease.

Changes To This Summary (07 / 21 / 2010)

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.

General CAM Information

Complementary and alternative medicine (CAM)—also referred to as integrative medicine—includes a broad range of healing philosophies, approaches, and therapies. A therapy is generally called complementary when it is used in addition to conventional treatments; it is often called alternative when it is used instead of conventional treatment. (Conventional treatments are those that are widely accepted and practiced by the mainstream medical community.) Depending on how they are used, some therapies can be considered either complementary or alternative. Complementary and alternative therapies are used in an effort to prevent illness, reduce stress, prevent or reduce side effects and symptoms, or control or cure disease.

Unlike conventional treatments for cancer, complementary and alternative therapies are often not covered by insurance companies. Patients should check with their insurance provider to find out about coverage for complementary and alternative therapies.

Cancer patients considering complementary and alternative therapies should discuss this decision with their doctor, nurse, or pharmacist as they would any therapeutic approach, because some complementary and alternative therapies may interfere with their standard treatment or may be harmful when used with conventional treatment.

Evaluation of CAM Approaches

It is important that the same rigorous scientific evaluation used to assess conventional approaches be used to evaluate CAM therapies. The National Cancer Institute (NCI) and the National Center for Complementary and Alternative Medicine (NCCAM) are sponsoring a number of clinical trials (research studies) at medical centers to evaluate CAM therapies for cancer.

Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a rigorous scientific process that includes clinical trials with large numbers of patients. Less is known about the safety and effectiveness of complementary and alternative methods. Few CAM therapies have undergone rigorous evaluation. A small number of CAM therapies originally considered to be purely alternative approaches are finding a place in cancer treatment—not as cures, but as complementary therapies that may help patients feel better and recover faster. One example is acupuncture. According to a panel of experts at a National Institutes of Health (NIH) Consensus Conference in November 1997, acupuncture has been found to be effective in the management of chemotherapy-associated nausea and vomiting and in controlling pain associated with surgery. In contrast, some approaches, such as the use of laetrile, have been studied and found ineffective or potentially harmful.

The NCI Best Case Series Program, which was started in 1991, is one way CAM approaches that are being used in practice are being investigated. The program is overseen by the NCI's Office of Cancer Complementary and Alternative Medicine (OCCAM). Health care professionals who offer alternative cancer therapies submit their patients' medical records and related materials to OCCAM. OCCAM conducts a critical review of the materials and develops follow-up research strategies for approaches deemed to warrant NCI-initiated research.

Questions to Ask Your Health Care Provider About CAM

When considering complementary and alternative therapies, patients should ask their health care provider the following questions:

  • What side effects can be expected?
  • What are the risks associated with this therapy?
  • Do the known benefits outweigh the risks?
  • What benefits can be expected from this therapy?
  • Will the therapy interfere with conventional treatment?
  • Is this therapy part of a clinical trial?
  • If so, who is sponsoring the trial?
  • Will the therapy be covered by health insurance?

To Learn More About CAM

National Center for Complementary and Alternative Medicine (NCCAM)

The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.

NCCAM Clearinghouse
Post Office Box 7923 Gaithersburg, MD 20898–7923
Telephone: 1–888–644–6226 (toll free) 301–519–3153 (for International callers)
TTY (for deaf and hard of hearing callers): 1–866–464–3615
Fax: 1–866–464–3616
Web site:

CAM on PubMed

NCCAM and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the Web sites of over 1,800 journals, allowing users to view full-text articles. (A subscription or other fee may be required to access full-text articles.) CAM on PubMed is available through the NCCAM Web site. It can also be accessed through NLM PubMed bibliographic database by selecting the "Limits" tab and choosing "Complementary Medicine" as a subset.

Office of Cancer Complementary and Alternative Medicine

The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via the NCI Web site.

National Cancer Institute (NCI) Cancer Information Service

U.S. residents may call the NCI Cancer Information Service toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 8:00 am to 8:00 pm. A trained Cancer Information Specialist is available to answer your questions.

Food and Drug Administration

The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.

Food and Drug Administration
5600 Fishers Lane
Rockville, MD 20857
Telephone: 1–888–463–6332 (toll free)
Web site:

Federal Trade Commission

The Federal Trade Commission (FTC) enforces consumer protection laws. Publications available from the FTC include:

  • Who Cares: Sources of Information About Health Care Products and Services
  • Fraudulent Health Claims: Don't Be Fooled
Consumer Response Center
Federal Trade Commission
Washington, DC 20580
Telephone: 1-877-FTC-HELP (1-877-382-4357) (toll free)
TTY (for deaf and hearing impaired callers): 202-326-2502
Web site:

About PDQ

PDQ is a comprehensive cancer database available on NCI's Web site.

PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at NCI's Web site. PDQ is provided as a service of the NCI. The NCI is part of the National Institutes of Health, the federal government's focal point for biomedical research.

PDQ contains cancer information summaries.

The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries are available in two versions. The health professional versions provide detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions provide current and accurate cancer information.

The PDQ cancer information summaries are developed by cancer experts and reviewed regularly.

Editorial Boards made up of experts in oncology and related specialties are responsible for writing and maintaining the cancer information summaries. The summaries are reviewed regularly and changes are made as new information becomes available. The date on each summary ("Date Last Modified") indicates the time of the most recent change.

PDQ also contains information on clinical trials.

A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.

Listings of clinical trials are included in PDQ and are available online at NCI's Web site. Descriptions of the trials are available in health professional and patient versions. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237).

Last Revised: 2010-07-21

If you want to know more about cancer and how it is treated, or if you wish to know about clinical trials for your type of cancer, you can call the NCI's Cancer Information Service at 1-800-422-6237, toll free. A trained information specialist can talk with you and answer your questions.

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