According to a CBC News report, ancient druids believed mistletoe had magical properties because of the way it grows, never touching the ground and without taking nourishment from the earth. However, University Hospital of Wales in Cardiff researchers are warning there is nothing magical about the use of mistletoe extract for the treatment of cancer, and in fact, it can cause harm.

Serious side effects from the injection of mistletoe extract have been reported in the Christmas issue of the British Medical Journal, including a case concerning a 61-year-old woman who had a tumor-like growth develop under her skin, brought on when she self-injected herself with mistletoe extract. The researchers warn that the use of mistletoe extract has been shown to cause a severe allergic reaction, breathing difficulties, joint pain and kidney failure. Some studies have shown that mistletoe might actually lead to cancer growth.

Edzard Ernst, a professor of complementary medicine at the Universities of Exeter and Plymouth is quoted as saying, "The idea that mistletoe may help treat cancer is based on that the idea that mistletoe, like cancer, is a parasitic growth that eventually kills its host." The researchers of this published study indicated that there are over 30 mistletoe extract preparations available in Europe, and its use by cancer patients is well-known.

From another source, the National Cancer Institute's overview of mistletoe includes the following:

• Mistletoe is a plant that grows on several types of trees and has been used since ancient times to treat many ailments.
• Mistletoe extract has been shown to kill cancer cells in the laboratory and to boost the immune system.
• Animal studies have suggested that mistletoe may be useful in decreasing the side effects of standard anticancer therapy.
• Many human studies using mistletoe to treat cancer have been done in Europe with unclear results, and a few clinical trials in the United States and abroad are in progress.
• Very few bad side effects have been reported from the use of mistletoe extract, though mistletoe plants and berries are poisonous to humans.
• The U.S. Food and Drug Administration (FDA) has not approved mistletoe as a treatment for cancer or any other medical condition.
  

To read detailed information about the highlighted overview, visit the NCI's FAQ about mistletoe.