There's little evidence that homeopathic remedies help to relieve side-effects of cancer treatments, but they also don't seem to cause serious interactions with conventional therapies, a new review concludes.

Drugs and radiation therapy given for cancer can cause side-effects such as nausea and vomiting, mouth sores, dermatitis, and menopausal symptoms.

It's estimated about a third of cancer patients use complementary therapies such as homeopathic medicines to try to reduce these side-effects, researchers said in Tuesday's Cochrane Database, which is published by an organization that evaluates medical research.

Lead researcher Dr. Sosie Kassab, of the Royal London Homeopathic Hospital in the UK and colleagues reviewed eight clinical trials that included 664 cancer patients.

Of the studies that were assessed, two pointed to potential benefits:

• Topical calendula, an extract from marigolds, may be helpful for skin inflammation from radiation therapy for breast cancer.
• A mouthwash called Traumeel S — a mix of various plant extracts and minerals — may help ease mouth sores caused by chemotherapy compared with a placebo.

"We found preliminary data that suggest there may be benefit associated with two homeopathic medicines in specific circumstances, although these results need to be replicated in further studies," Kassab said in a release.

"The effects of calendula may also depend on the formulation, as it can be prepared using a range of different methods."

None of the homeopathic medicines studied reported serious side-effects or interactions with conventional treatments.

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The calendula study included 254 people with breast cancer who were getting radiation treatments and were randomly assigned to take the extracts or a standard ointment to prevent dermatitis.

Those in the calendula group suffered less skin inflammation during their radiation treatment.

The Traumeel S study looked at 32 children undergoing chemotherapy who were randomly assigned to use either the mouthwash or a placebo rinse.

Children in the herbal rinse group generally had less severe mouth inflammation.

Currently, there is "no convincing evidence" to support the use of homeopathic medicines for other side-effects of cancer treatment, Kassab cautioned.

Patients should discuss the use of homeopathic medicines alongside radiotherapy and chemotherapy with doctors, since there may be guidelines on what should not be taken, she added.