The anti-wrinkle capsules, which have generated a large demand on the continent, contain a powerful cocktail of chemicals designed to prevent and repair skin damage caused by sunlight, pollution and cigarette smoke.

The main ingredients in the Oligomeric Pro Anthocyanidolic (OPC) capsules are grape-seed polyphenols - antioxidant chemicals found in red wine, 50 times more powerful than vitamin E and 25 times more effective than vitamin C.

Scientists believe that antioxidants can prevent skin damage, and repair the damage to cell walls and blood vessels already caused by the ageing process.

It is known that antioxidants mop up harmful molecules called free radicals, which are a major cause of the appearance of ageing.

These restore elasticity in the skin and help prevent free-radical damage.

Their effect is enhanced by borage and primrose oil, which both contain chemicals that revitalise the skin.

Primrose oil has also been shown to alleviate pre-menstrual and menopausal symptoms.

Matilde Thomas is managing director of OPC manufacturers Caudalie Laboratoires in Paris.

She said: "Inevitably with time your skin begins to show the first tangible signs of ageing and general wear and tear, and these symptoms are exacerbated by exposure to ultra-violet rays from the sun and periods of stress.

"Caudalie's OPC capsules act as `time machine tablets' which simultaneously delay wrinkles and promote vitality in the skin. The fusion of polyphenols and oils helps to balance out skin deficiencies linked to hormonal changes and protects against the sun, pollution and smoking."

Doctors sceptical

Powys GP Dr John Buchan, a member of the Primary Care Dermatology Society, warned that there was little scientific proof that antioxidants did reverse the impact of ageing.

"Antioxidants are of dubious benefit. The claims made by cosmetics manufacturers have not borne fruit in clinical trials," he said.

"The ageing process is a cumulative process, determined solely by the amount of exposure to the sun.

"If you want to prevent yourself from further ageing - and reduce the risk of developing skin cancer - the best way to do it is to protect yourself from the sun."

Dr Katharine Dalziel, assistant secretary of the British Association of Dermatologists, said: "It is exceedingly unlikely that antioxidants taken by mouth are going to get to the skin in a sufficient metabollically active concentration to make a big difference."