Written by Katja Boehm and the CAM-Cancer Consortium.
Updated February 8, 2017


What is it?

Scientific name / brand name / common name

Essiac tea has been used for over 70 years as a remedy for the adverse effects caused by conventional cancer treatments and supposedly for curing cancer itself. The name ‘Essiac’ was created by the Canadian nurse Renée M. Caisse (‘Essiac’ is ‘Caisse’ spelled backwards)1-3. Other Essiac products are known as Flor-Essence®.


The four herbs contained in Essiac® are:
• Burdock root (Arctium lappa L.),
• Indian rhubarb root (Rheum officinale L.),
• Sorrel (Rumex acetosa L.)
• Slippery elm bark (Ulmus rubra/fulva Muhl.)

A modified Essiac product (Flor-Essence®) also includes the following four additional herbs:
• Watercress (Nasturtium officinale L.),
• Blessed thistle (Centaurea = Cnicus benedictus L.),
• Red clover (Trifolium pratense L.) and
• Kelp (Laminaria digitata).

History / providers

According to Renée Caisse, an English miner’s wife had received the recipe for Essiac from a Native Ojibwa Indian medicine man, and had cured her breast cancer with this treatment. Renée Caisse, who worked at the Bracebridge Cancer Clinic in Ontario, Canada from 1935 to 1941, treated cancer patients with Essiac herbal tea for 50 years.

In 1938, concerns about the use of Essiac were raised, after evidence of one reported death and one report of toxicity after Essiac tea injections emerged4,5. In 1941, the Bracebridge Cancer Clinic was closed following a request by the Canadian authorities. Between 1959 and 1978 Caisse worked with Dr Charles Armao Brusch, director of the Brusch Medical Clinic in Cambridge, Massachusetts, in the US, to modify the original recipe and promote the use of Essiac. After carrying out some laboratory studies on mice, four further herbs were added to the recipe (see above) to improve the healing action and taste of Essiac. In 1977 Mrs Caisse sold the original Essiac recipe to Resperin Corporation Ltd of Toronto, Canada.

In 1982 the Resperin Corporation Ltd carried out some poorly designed trials in which physicians using the product were asked to submit case reports. The Canadian Department of National Health and Welfare terminated the tests, claiming that Resperin had conducted a poorly conceived and executed investigation. Health Canada concluded that the evidence was unconvincing and that there was no scientific evidence to support claims that Essiac could cure cancer6. However, under the Canadian Emergency Drug Release Programme, Essiac could be obtained on physician’s request. In 1995 the Essiac formula and its trademark were purchased from Resperin Corporation Ltd by David Dobbie. Thus, Essiac® Products Inc of New Brunswick became the manufacturer of Essiac®. Another Canadian product, Flor-Essence®, is manufactured in British Columbia, where Charles Armao Brusch is involved in using the eight herbs of the modified Essiac formula. Nowadays, more than 40 different formulas of Essiac are available globally.

Claims of efficacy / mechanisms of action / alleged indication

Renée Caisse documents her view of how Essiac affects the cancer process as follows: after enlarging and hardening of the tumour following the first few treatments, tumour softens and, if the tumour was located near an exterior route, the patient discharges large amounts of pus and fleshy material. She believed that somehow Essiac would cause cancerous cells to retreat to the site of the original tumour where they would then shrink and vanish.

Charles A Brusch claimed that Essiac works by identifying toxins, gathering them, breaking them down and discharging them. He also suggested that in an unpublished double-blinded study carried out by his institute, positive results were observed including pain cessation, increased appetite, improved sleep, well-being and energy, decreased depression, anxiety and fear and a decrease in nodular masses.

The explanations put forward for a mechanism of the therapy are not supported by good evidence, nor are they deemed a possible and sufficient explanation by current scientific standards.

Application and dosage

The tea is usually taken 1-3 times before meals to minimise possible adverse effects such as nausea, vomiting and diarrhoea. Initially, Caisse administered one of the herbs by injection and gave the others as tea. Nowadays, most products are in tea form but other products also exist in the form of drops, capsules, liquids and dry versions. The patient is supposed to boil the mixture and then drink the tea. The patient information also advises that no other treatment, including chemotherapy and radiotherapy, should be used while taking Essiac.

Prevalence of use

In 1982 when Canadian health officials conducted a retrospective review of Canadian patients treated with Essiac they found that about 150 physicians in Canada had at that stage reportedly requested supplies of Essiac on behalf of their cancer patients7. In a Canadian survey from 2000 among women with breast cancer 15% reported using Essiac (ResperinTM, Canada Limited)8. Two further surveys were carried out in the USA and targeted specifically at Flor-Essence® users in order to quantify its use, it was found that among the 5051 respondents 22% were diagnosed with breast cancer9,10. Finally, in a survey at the Royal Marsden Hospital in London, UK 318 cancer patients were asked about their use of Essiac and 6% reported using Essiac11.

Legal issues

Essiac cannot be marketed as a drug because it has no licence. It is therefore usually sold as a nutritional supplement. In Canada, Essiac is currently unapproved for marketing and cannot be used in clinical trials without a valid preclinical new drug submission. However, the Canadian government allows Essiac to be manufactured and sold. Manufacturers are not allowed to make any medical claims, instead Essiac is promoted as a health-enhancing herbal tea. Patients who wish to obtain Essiac must ask their physician to make a request to the Canadian Bureau of Human Prescription Drugs, which relays the order to the company and the company then ships it directly to the patient.


Essiac products vary in price from €4.15 to hundreds of Euros per month for pre-made bottled blends. A pre-fabricated Essiac tea can range from €15.00 to €24.00 per ounce bottle. A higher price does not necessarily indicate higher quality of the product.


Katja Boehm, CAM-Cancer Consortium. Essiac [online document]. http://cam-cancer.org/The-Summaries/Herbal-products/Essiac. February 8, 2017.

Document history

Assessed as up to date in February 2017 by Barbara Wider.
Assessed as up to date in April 2016 by Barbara Wider.
Assessed as up to date in January 2015 by Barbara Wider.
Assessed as up to date in February 2013 by Katja Boehm.
Fully revised and updated in December 2011 by Katja Boehm.
Fully revised and updated in August 2009 by Katja Boehm.
Summary first published in May 2005, authored by Katja Boehm and Edzard Ernst.


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