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]). Reviewed in [2-10] 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.). Reviewed in [2-4,7]
The manufacturers of Essiac and Flor Essence both claim they market the original herbal mixture promoted by the developer.[1,11] Although only one company manufactures Flor Essence, several companies produce and market Essiac-like products. Reviewed in [2,3,10] 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.[1,11] Reviewed in [4,6,7,9] Proponents of Essiac further claim that it helps relieve pain, improves overall quality of life, may reduce tumor size, and may prolong the survival of patients with various types of cancer. Reviewed in [4,7,9] 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). Reviewed in [2-4,9,13-16] It is said that the benefits of Essiac and Flor Essence are dependent on the presence of the constituent herbs in the correct proportions. Reviewed in [2-4,9] 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. Reviewed in  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. Reviewed in  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.[1,11] Reviewed in [2-4,10] 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.[1,11] Reviewed in [4,6,8,9,18] 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. Reviewed in [4,8,9,18]
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 a day, depending on individual requirements, and that it may be used on an ongoing basis. 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. 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 at this time.
The manufacturers of Essiac and Flor Essence both state these products can be used in conjunction with other cancer treatments.[1,11] 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. Reviewed in  The purported rationale for this statement is that conventional anticancer treatments may alter immune system function and prevent Essiac from working effectively. Reviewed in  As indicated previously, no evidence has been reported in the peer-reviewed scientific literature to show that Essiac is an effective treatment for patients with cancer.
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- Essiac. Toronto, Canada: Canadian Breast Cancer Research Alliance, 1996.
- The History of Essiac & Rene Caisse, Canada's Cancer Nurse. Kirkland, Canada: Altramed Health Products, 2001. Available online. Last accessed August 10, 2012.
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- Ottenweller J, Putt K, Blumenthal EJ, et al.: Inhibition of prostate cancer-cell proliferation by Essiac. J Altern Complement Med 10 (4): 687-91, 2004. [PUBMED Abstract]
- LeMoine L: Essiac: an historical perspective. Can Oncol Nurs J 7 (4): 216-21, 1997. [PUBMED Abstract]
- Bennett LM, Montgomery JL, Steinberg SM, et al.: Flor-Essence herbal tonic does not inhibit mammary tumor development in Sprague Dawley rats. Breast Cancer Res Treat 88 (1): 87-93, 2004. [PUBMED Abstract]