Firms which make herbal medicines must now get their products approved by an independent agency after the introduction of a new law.
Herbal medicines face greater regulation under the directive
The EU directive, designed to ensure that people who buy the products will have a guarantee of their quality and safety, came into effect on Sunday.
Until now, the government says, consumers have not known which herbal remedies are of an acceptable standard.
Companies will now have to provide evidence of a new product's safety.
Before new remedies can be registered and sold, information about how they should be used must also be approved.
The government adds that before the directive was introduced, reputable companies following high standards were left at a commercial disadvantage while consumers were potentially at risk from unsafe products.
Last month, a report commissioned by the Prince of Wales said that complementary therapies, including herbal medicines, should be given a greater role in the NHS.
The report, by economist Christopher Smallwood, said patients with conditions such as back pain and stress can benefit from some of the therapies.
And back in August, a leading patients' group called for access for all to alternative medicine on the NHS.
The Patients Association called for all GPs to provide patients with the choice of using complementary medicine where it had been proven to work.
Provision is patchy currently with well under a half of family doctors providing some sort of access to alternative therapies.