Garlic, ginger and ginkgo capsules, for instance, can delay the therapeutic of skin wounds when breast cancer spreads.
Surgeon Prof Maria Joao Cardoso, mentioned there was no proof that natural therapies or lotions labored.
If unsure, it was greatest to not take something, she stated.
“Docs must be extra proactive about asking their patients what else they’re taking when they’re being handled for cancer,” Prof Cardoso, head breast surgeon on the Champalimaud Cancer Centre in Lisbon, Portugal, advised the BBC.
She mentioned it was particularly vital that patients at all times checked with their medical doctors first earlier than attempting complementary therapies for most cancers that had unfold to the skin.
This occurs in a single in five instances of breast most cancers – and fewer in different cancers.
The hazard is that many merchandise can intrude with hormone remedy or chemotherapy therapies, and sure ones lengthen the blood clotting course of – which might result in wounds taking longer to heal and extra scarring.
Prof Cardoso mentioned it was not stunning that sufferers and their carers went looking for complementary or different remedies which may make a distinction.
However she stated folks ought to know “they might find yourself doing extra hurt than good”.
“The best purpose in drugs is essential to recollect: do no hurt,” she stated.
On its web site, Cancer Research UK says some complementary therapies may cease typical remedies working in addition to they need to.
It additionally says it is very important keep away from some meals and drinks equivalent to grapefruit and oranges throughout most cancers therapy, as a result of they’ll have an effect on how properly most cancers medicine are damaged down within the body.