There are call for better labelling of herbal medicines sold in Australia after a review identified a risk of adverse interactions with conventional drugs.

Some commonly used herbal medicines may contain "toxic" ingredients that interact adversely with other medications, putting people at risk.

An Australian review of traditional herbal preparations led by medical researchers at the University of Adelaide found toxic chemicals, heavy metals and pesticides.

The review published in the Medical Journal of Australia also found common products like St John's Wort and evening primrose oil can react cause bad reactions when mixed with prescription medicines and interfere with the outcome of surgical procedures.

Nearly 70 per cent of Australians use herbal products, but more than half don't tell their doctors.

"Not only can herbal medicines interact with traditional pharmaceutical medicines but also with other herbal medicines the patient may be using," UoA amolecular pharmacologist and toxicologist Dr Ian Musgrave said.

St John's wort, or Hypericum perforatum is used to relieve nervous tension and stress. But it can also cause acute transplant rejection and "intermenstrual" bleeding in women using oral contraceptives.

Asian ginseng can adversely interact with immunosuppressant drugs, while evening primrose has been shown to lower the seizure threshold in people with epilepsy and interfere with anti-epileptic medications.

Study lead author and Professor of Pathology at UOA Roger Byard said there was a "mistaken belief" that "natural" means "safe".

He's calling for tighter controls on sales of herbal medicines and wants better labelling.

"The lack of systematic observation has meant that even serious adverse reactions, such as the kidney failure and liver damage caused by some plant species, have gone unrecognised until recently," he said "We feel it would be appropriate for the Therapeutic Goods Administration to require manufacturers to have samples independently tested before placing them on the market."

But the TGA said Australia already had an "internationally well regarded" regulatory system for all medicines, including herbal and other complementary medicines.

"The authors point largely to examples of problems from overseas," a spokesperson said in a statement on Monday.

"Where the TGA has come across adulterated herbal medicines these have been illegally imported and are not supplied via the usual retail outlets but are generally purchased over the internet."