Mistletoe should be reserved for Christmas decorations only and not used as an anti-cancer drug, say doctors cited in a journal article this week. They found that cancer patients who injected themselves with extracts of the plant suffered serious side-effects.

In this week's Christmas issue of the British Medical Journal, Alison Finall of the department of histopathology at University Hospital of Wales in Cardiff and her colleagues reported on a case of a 61-year-old woman who had a tumour-like growth under her skin, brought on by mistletoe.

Ancient druids believed mistletoe had magical properties because of the way it grows, never touching the ground and without taking nourishment from the earth.
(Christopher Furlong/Getty Images)

The woman, who had previously been treated for cancer and was worried the growth was a recurrence, had injected herself with the extract. The tumour was actually a reaction to the mistletoe.

The woman's case spurred the researchers to investigate the medical use of mistletoe further.

Thousands of internet sites mention mistletoe as a cancer treatment and at least 30 different mistletoe preparations are available in continental Europe, the study's authors said. Thus, some patients with cancer inject themselves with mistletoe in the hopes of improving their condition.

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, said Edzard Ernst, a professor of complementary medicine at the Universities of Exeter and Plymouth.

Serious side-effects may occur

However, the most reliable randomized controlled trials fail to show benefits of mistletoe, and there are reports of considerable potential for harm, including anaphylaxis (severe allergic reaction), breathing difficulties, joint pain and kidney failure.

Furthermore, some test tube studies suggest that mistletoe extract may actually enhance the growth of some cancers.

The costs of regular mistletoe injections are also high, Ernst said.

Mistletoe is a woody perennial that grows on several species of tree, including elm, apple, pine and oak. It is used as a Christmas decoration in the United Kingdom. Traditionally, anyone who lingers under the decoration is kissed.