Health-store junkies stock up regularly on herbal remedies such as milk thistle to beat hangovers, St John's wort for anxiety and feverfew to prevent migraines. Others are more sceptical about their effects, but a new study published in the Lancet last week provides the strongest evidence yet that echinacea, the controversial herbal remedy, works. A substantial review of 14 studies found that echinacea can reduce the chance of catching a cold by 58% and, should you get one, shorten its length by 1.4 days. Enough, surely, to plant a smug grin on the face of the estimated one in five adults in the UK who uses herbal medicines.

That so many place their trust in herbal remedies is hardly surprising - how much more pleasant to ingest a treatment that is part of a centuries-old tradition, derived from the natural world and named after a plant, than to swallow a capsule of synthetic chemical compounds produced by a faceless, monolithic conglomerate. But while herbal remedy consumers swear by arnica for bruises and insist that valerian is as good as any sleeping pill, they might be less content to learn that the herbal remedies market in the UK is at present almost entirely unregulated. There is no independent assessment of any herbal product's quality and safety before it goes on sale and neither are there any regulations covering the information provided with products.

"At the moment a lot of herbal products are of a low standard," says Dr Dick Middleton, former chairman of the British Herbal Medicine Association and technical director of the herbal remedy company MH Pharma (UK). "There are few checks on the manufacturing process and there is often even no batch-to-batch consistency. It makes it difficult to know or to recommend which products to take, because while there are some high-quality remedies, you don't necessarily know which ones they are."

Medical herbalist and lecturer Daniela Turley says: "I know of tests that have been done on products that sometimes show that the remedy didn't even contain an active ingredient. Sometimes the herb in them isn't even the advertised herb. And big companies can be guilty of this."

The situation is set to change. EU legislation introduced in 2005 means that by April 2011 all herbal remedies on sale in this country will have to be independently assessed by the Medicines and Healthcare Products Regulatory Agency (MHRA) before receiving official registration. "Manufacturers will have to submit a dossier of evidence supporting the quality and safety of their product," says Richard Woodfield, head of herbal policy at the MHRA. "They'll also have to provide thorough information with the product when it's sold and submit to an inspection of the manufacturing site."

But it is only now, two years after the legislation was introduced, that the first registered products are going on sale. At present, there have been 21 applications to register a product and three licences have been granted - two of them to MH Pharma products. One, FlexiHerb, is a devil's claw remedy to relieve back pain, and another, MigraHerb, is based on feverfew.

With hundreds of herbal products on sale, serious catching up will be necessary before 2011. "Some retailers are worried that some products will no longer be available in 2011," says Jane Gray, vice-president of the National Institute of Medical Herbalists. "A lot of the products come from small companies and whether they will be able to cope with the legislation I don't know, but it could put quite a lot of products at risk."

While practising medical herbalists will still be able to prescribe and provide patients with their own remedies, by 2011 they might find some resources no longer available to them. "At the moment, if a patient says that they want to try a herb, I could make them up another medicine myself," explains Gray, "or I could recommend a product from a reputable company that's on sale at the health store. But that could be limited as a result of the legislation."

The situation is complicated by the fact that herbal remedies often contain more than one herb - valerian is often combined with hops for insomnia, for example, and echinacea with cat's claw and eucalyptus for extra potency. "I think if any of the remedies drop away, it will be the combination treatments," says Turley. "It's not difficult to test one remedy, but when you're combining them it's more difficult."

It seems unlikely, meanwhile, that the new rules will settle the ongoing debate over whether herbal remedies are actually any good. The aim is to standardise and improve the quality of herbal remedies on sale, not to prove that they work. "When it comes to the requirements for demonstrating effectiveness in medicines, the bar has been raised," explains Middleton. "It is quite hard to get a conventional medicine licensed and it costs millions of pounds. The companies that produce herbal remedies are small and it would be very difficult for them to carry out clinical trials."

To circumvent this problem, manufacturers will not be required to prove that their herbal product works, only that people have historically believed that it did. "A licence does not depend on checking for efficacy," says Middleton, "but a manufacturer will have to demonstrate that the herb has been used for 30 years, and at least 15 years in Europe."

But no amount of registration can stop people self-diagnosing. "Patients do buy inadvisable or inappropriate remedies," says Jane Gray. "I've also overheard people being given bad advice in health shops. Herbalists are trained and we know what herbs to take, in what doses, and which ones to take in conjunction with other medicines." She would always advise someone who wants to take herbs to see a trained herbalist.

Supporters of the new deal point out that it will require better information to be available to over-the-counter customers, which might mean that some of the more ill-advised herbal regimes or combinations of traditional and herbal medicines are avoided. (Most herbs have contra-indications. Angelica, for example, isn't recommended for people who have peptic ulcers or who are pregnant.) They also believe that there is plenty of time for the herbal remedy industry to adhere to the new standards.

"It's still early days," says the MHRA's Richard Woodfield, "and some of the information required for the dossier will take time to collect. We don't underestimate the challenge to companies but we are trying to encourage them as much as possible to apply for registration." Middleton concedes that the scheme has had a slow start. "But that's not surprising given the magnitude of what's involved."

In any case, the hard work may pay off. Middleton believes that the legislation could help make herbal remedies more mainstream. "I think it will mean that medical herbalists are more likely to be accepted as partners in primary care," he says.

Woodfield agrees. "If you are a doctor in conventional medicine you cannot be sure that a herbal remedy has got in it what it says it has. It's bound to hold back confidence." He points to countries such as Germany that already have a good system of regulation, and where herbal remedies are taken more frequently. St John's wort, for example, is prescribed more commonly than synthetic antidepressants for mild depression by German doctors.

Turley believes that overall legislation will have a positive effect on the reputation of medical herbalism. "Even if it's just someone taking a remedy and deciding that herbs don't work, because the remedy they took was made out of useless powder from the bottom of a barrel," she says. "If that stops, it will be a good thing. But there are still a lot of grey areas to work out before 2011."