Many herbal remedies on sale in the UK lack important safety information, researchers have warned.
A new EU law which came into force in April this year requires herbal medicinal products to be licensed, or to get Traditional Herbal Registration (THR), which means the information with the product has been approved.
The information provided with the herbal product should clearly explain the risk of side effects and possible interactions with prescribed medicines.
Researchers from the University of Leeds investigated the safety information supplied with 68 different preparations of five common herbal remedies: St John’s wort, Asian ginseng, Echinacea, garlic and Ginkgo.
The products were chosen because they can cause potentially harmful effects in some people.
St John’s wort can reduce the effectiveness of the contraceptive pill and can also affect warfarin, a drug used to prevent blood clotting.
Asian ginseng is not suitable for people with diabetes and Ginkgo and Echinacea can cause allergic reactions.
Even garlic can cause problems for some people as it can thin the blood and interfere with drugs used to treat HIV, the researchers said.
The study found that 93 per cent of the products looked at were unlicensed, which meant they did not have to meet any safety or quality standards, and over half were marketed as food supplements.
Only 13 per cent contained an information sheet and just three contained an acceptable amount of safety information.
Theo Raynor, professor of pharmacy at the university, said: “Consumers need reliable and comprehensive information when buying herbal remedies – information which tells them whether the remedy is suitable for them.
“I would advise anyone buying a herbal medicine to check the box or packaging contains the ‘THR’ logo, which shows that the information it comes with has been approved.
“Herbal medicines should, ideally, be purchased where trained staff are available, so that consumers can have any questions answered. This information should be available from pharmacists.
“People should also always tell their doctor about herbal medicines they are taking, so they receive the best possible care.”
The study is published in the journal BMC Medicine.