The Medicines Control Agency is investigating the claim, made in the British Medical Journal, by researchers from King's College Hospital, London.

The researchers, led by Dr Fiona Keane, a specialist registrar in dermatology, have called for closer regulation of herbal medicines.

No warnings

Dr Keane's team found that eight of 11 creams tested contained the prescription-only steroid Dexamethasone. Most of the creams were designed for the treatment of eczema.

The concentration of the steroid in the creams prescribed for children was 5.2 times higher than in those prescribed for adults.

The concentration used in all eight remedies was inappropriate for use on the face.

No warnings about the side-effects of using such potent steroids inappropriately or on thin skin, such as the face, was given to any of the patients.

Potential side-effects include:

• Permanent thinning of the skin, particularly if used on the face, or behind joints such as the elbow and knee

• Permanent stretch marks, known as striae

• Prominent blood vessels, a condition known as telangiectasia

• Easy bruising

• Increased risk of skin infections

Dr Keane and colleagues acknowledged that their study was based on a small sample in one area of London.

Tighter restrictions

However, they conclude that their findings suggest a need for greater regulation and restriction to be imposed on herbalists.

They also called for continuous monitoring of the side-effects of such medications.

The skin behind the knees is sensitive

Dr Keane said: "Many people go to herbal practices so they don't have to use the steroids they would get from a GP or dermatologist.

"They assume they are getting natural products, but in some cases they were getting higher levels of steroids than they would get from a GP or a dermatologist."

A MCA spokeswoman said: "The growth in the market for traditional Chinese medicines is something the MCA is focussing on, and any reports of illegal activities will be investigated."

Jonathan Monckton, director of the Research Council for Complementary Medicine, called for statutory reglation to be extended to cover most branches of complementary practice.

He said: "Complementary treatments need to be researched and should not just be allowed to go on haphazardly.

"This kind of thing is devious, manipulative and exploitative and nothing to do with medicine, either traditonal or complementary - it is just bad practice."