Cancer patients have been advised to tell their doctors if they are taking herbal products.

This is because some of the ingredients could stop their treatment from working properly.

According to the BBC, a cancer conference made this note .

For instance, reports say garlic, ginger and ginkgo pills, can delay the healing of skin wounds when breast cancer spreads.

A Surgeon, Professor Maria Joao Cardoso, head breast surgeon at the Champalimaud Cancer Centre in Lisbon, Portugal, told the BBC. that there was no evidence that herbal therapies or creams worked.

According to her If in doubt, it was best not to take anything, she said.

She further stressed that “Doctors need to be more proactive about asking their patients what else they are taking when they are being treated for cancer,”

She said it was particularly important that patients always checked with their doctors first before trying complementary therapies for cancer that had spread to the skin.

This happens in one in five cases of breast cancer – and less in other cancers.

The danger is that many products can interfere with hormone therapy or chemotherapy treatments, and certain ones prolong the blood clotting process – which can lead to wounds taking longer to heal and more scarring.

She however highlighted the following herbal products as examples of those which slow down clotting:

green chiretta

feverfew

garlic

ginkgo

ginseng

hawthorn

horse chestnut

turmeric

The Professor said it was not surprising that patients and their carers went searching for complementary or alternative treatments that might make a difference.

But she said people should know “they could end up doing more harm than good”.

“The highest goal in medicine is important to remember: do no harm,” she said.

On its website, Cancer Research UK says some complementary therapies might stop conventional treatments working as well as they should.

It also says it is important to avoid some food and drinks such as grapefruit and oranges during cancer treatment, because they can affect how well cancer drugs are broken down in the body.