Cancer patients should tell their doctors if they are taking herbal products because some of the ingredients could stop their treatment working, a cancer conference has heard.
Garlic, ginger and ginkgo pills, for example, can delay the healing of skin wounds when breast cancer spreads.
Surgeon Prof Maria Joao Cardoso, said there was no evidence that herbal therapies or creams worked.
If in doubt, it was best not to take anything, she said.
“Doctors need to be more proactive about asking their patients what else they are taking when they are being treated for cancer,” Prof Cardoso, head breast surgeon at the Champalimaud Cancer Centre in Lisbon, Portugal, told the BBC.
She said it was particularly important that patients always checked with their doctors first before trying complementary therapies for