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The safety of herbal products and medicines

Information on how safe herbal health products and medicines are.

What herbal medicine is

Herbal medicine uses plants, or mixtures of plant extracts, to treat illness and promote health. It's sometimes called phytomedicine or phytotherapy.

Herbal medicine is one of the most common complementary and alternative therapies used by people with cancer. Some studies show that they use herbal medicine alongside conventional medical treatments such as radiotherapy, chemotherapy or biological therapy.

Herbal medicines and cancer

Many herbal medicine products (or herbal remedies) can be bought over the counter and are marketed as natural or herbal. There is some evidence that herbal products can help to prevent or relieve some symptoms of cancer and the side effects of treatment.

Using herbal remedies during cancer treatment

Talk to your cancer doctor, specialist nurse, GP or pharmacist before having any type of herbal remedy. They are medicines. And like any medicine, they have effects on the body and can cause side effects.

It's very important to use only herbal products that are registered under the Traditional Herbal Remedies (THR) scheme. Remedies that are registered under the scheme have a THR mark and symbol on the packaging. THR products have been tested for quality and safety.

Some herbal remedies might interact with cancer treatments such as chemotherapy, radiotherapy, biological therapy or hormone therapy. Some herbal remedies could make particular cancer drugs work less well or may increase the side effects.

We don't yet know very much about these interactions or side effects. So we need results from large clinical trials to show which herbs are safe to use alongside conventional treatment.

Last reviewed: 
24 Oct 2014
  • Oxford Textbook of Palliative Medicine (3rd edition)
    D Doyle, G Hanks, N Cherny and K Calman
    Oxford University Press, 2005

  • Medicines and Healthcare Products Regulatory Agency (MHRA)
    Public Assessment Reports
    Accessed October 2014

  • Herb-drug interactions: a literature review
    Z Hu and others
    Drugs, 2005. Volume 65, Issue 9

  • Spontaneously reported adverse reactions in association with complementary and alternative medicine substances in Sweden
    I Jacobsson and others
    Pharmacoepidemiology and Drug Safety, 2009. Volume 18, Issue 11

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