If taken incorrectly, herbal medicines can lead to allergies, liver or kidney malfunction, blindness, cancer or even death. Surprised? Find out why you should exercise caution when popping your favourite herbal remedy.

In 2007 alone, Brits will invest £191 million in complementary medicines – a 32% increase in sales since 2002. And by 2011, complementary healthcare sales will break the £250 million barrier, according to figures from Mintel. But are herbal remedies really that natural – and what are the dangers of mixing them? We spoke to Dr Lakshman Karalliedde, co-author of new book Traditional Herbal Medicines: A Guide To Their Safer Use, about why you could be getting a dose of Viagra or arsenic with your daily plant fix – and why herbal medications should be made available on the NHS.

Why are herbal remedies becoming so popular?

Herbal medicines have been a tradition for thousands of years, while western medicine has only been developed for the last 200 years. Now why would people go back to traditional medicine? I think it’s part of the global movement to go green and natural. There is a perception that anything natural or green is safer and less toxic.

Also, herbal medicines are usually provided by practitioners who spend time asking patients questions and helping them in a subjective way. We in western medicine have limited time and listen less to our patients than traditional practitioners, who have a more holistic approach.

What are some of the risks involved in using herbal medicines?

There are many. I have a lot of respect for traditional medicine, and the science is not at fault. It’s the manufacturers and practitioners who have made the mistakes. One of the risks is that there is no consistency in the dosage and method of administration – it varies from country to country and practitioner to practitioner. Secondly, in the manufacture and preparation of herb products there is a high risk of contaminants – heavy metals like lead, mercury and arsenic. People think that herbal medicines are completely natural, but most use a combination of herbal medicines and these are mixed in a way that increases the risk of contaminants – for example, plants from certain geographical areas are full of pesticides and heavy metals.

But the biggest danger I think is the fact that herbal medicines contain more and more western drugs, some of which have been banned in countries like the UK and US – for example Viagra, amphetamines and steroids, sometimes in a modified form. They’re also added in quantities that would be considered toxic by those of us practicing western medicine, particularly with herbal preparations used for slimming and sexual disorders.

What are the risks of people who don’t know much about herbal medicines self prescribing?

They don’t know exactly what they’re taking, and that can be very dangerous. There are conditions like acute appendicitis and brain tumours for which only surgery and western treatment provides a cure or relief. And people can have a serious disorder which goes undiagnosed and worsens while they take medication they are told will cure them.

Often, people don’t reveal herbal medications they are taking to their doctor – but some herbs increase toxicity or undermine the effectiveness of other medications. We had one person who bled for a long time after a hip operation and we didn’t know what on earth was going on. Eventually we found he was on a herbal treatment. There are certain traditional remedies that should not be taken before operations, during pregnancy and breastfeeding, or by diabetics or people prone to allergies.

Herbal remedies have been in the news lately because of new legislation that says they have to be safe, but don’t have to actually be medically effective – do you think there are many products out there that don’t work?

I’m sure there are. With traditional remedies, efficiency is unproven and usually anecdotal. Having been a doctor for over 40 years, I believe patient safety and comfort should be our primary aim. The fact that traditional practitioners spend a lot of time on their patients and take a holistic approach is something western medical practitioners can learn from. But what traditional healers can learn from us is that there must be investigations, repeated measurements, and parameters to show that medications are effective and safe. We should combine the two. For example, there are certain patients with malignancies who are on very powerful drugs like chemotherapy. Some of the adverse side effects cannot be effectively controlled by western medicine, but there are herbal preparations that can be used. I would like to see developed countries exposing medical students to traditional medicines, showing their strengths and weaknesses – there’s only one department of traditional medicine in the UK, at Exeter.

Do you think herbal remedies should be available on the NHS?

There are many western medicines that have been developed from herbs, including aspirin. One of the problems with any health system is the increasing cost of drugs, and I’m sure there are plant products that could be incorporated into the NHS as a more affordable option. Around 80% of people in the world use traditional remedies because of the cost.

What would you say are the top 5 most effective herbs?

St John’s Wart as an antidepressant, Echinacea to increase immunity, valerian to help sleep, lavender to help calm and relax, and ginkgo and ginseng to increase strength, resistance and performance. They are all very popular around the world.

Dr Lakshman Karalliedde is a toxicologist for the Health Protection Agency’s Chemical Hazards and Poisons Division and co-author of Traditional Herbal Medicines: A Guide To Their Safer Use, the new herbal compendium covering traditional herbal remedies from around the world, describing their sources, known effects and side effects, dosages, interactions and – most importantly – precautions. It’s a must for anyone involved in prescribing either conventional or traditional herbal medicines – as well as the growing number of people who are taking them.

Traditional Herbal Medicines: A Guide To Their Safer Use is published by Hammersmith Press, £19.99.

Many experts believe herbs can help in the treatment of stress related illnesses and can even protect against heart disease and cancer. To read more, Click Here.

To find out more about the uses of some common herbs, Click Here.