Millions of women who receive a pot of expensive skin cream this Christmas may find that the products do not live up to the marketing hype.

Leading cosmetics companies are making claims about the rejuvenating properties of their best-selling products that are scientifically incomprehensible and insult customers’ intelligence, pharmacists say.

Adverts for the creams, featuring actresses such as Penélope Cruz and Sarah Jessica Parker, promise to “refuel surface skin cells” and give skin “a dewy glow”, using scientific terms to back up these claims.

The market for so-called “cosmeceuticals”, cosmetics sold on the strength of their supposed scientific credentials, has doubled in the past five years to about £102 million. But most scientists say there is little evidence to suggest that claimed “active” ingredients such as pentapeptides, lipopeptides, hyaluronic acid and omega 3 have a beneficial effect on the skin.

Manufacturers are blinding consumers with science to the extent that even their own customer services departments cannot give accurate explanations of how these products work, Which?, the consumer organisation, found. In fact, so-called “nanoparticles” included in some products may actually be harmful, and should be avoided, dermatologists suggest.

Posing as consumers, researchers from Which? contacted customer services departments of the leading brands Garnier, L’Oréal and Olay, to ask how the claimed active ingredients in their products actually worked on the skin. The researchers asked about three products: Olay Regenerist Serum (RRP £22.50 for 50ml), Garnier Nutritionist Omega Skin (£12) and L’Oréal Dermagenesis (£18.99).

They then showed recorded transcripts of the conversations to Sense About Science, a charity that promotes accuracy in science, to see what it thought of the information. Experts concluded that the companies were often fobbing off customers with spurious or misleading information.

For example, when asked what was the hyaluronic acid contained in the L’Oréal moisturising cream, the company’s customer service representative incorrectly stated: “It’s not an actual acid,” before adding, “The product replumps, tautens and illuminates to give a radiance to the skin.”

Gary Moss, a pharmacist from the University of Hertfordshire, dismissed this explanation as “utter waffle”.

While the US Federal Drug Administration has approved the use of hyaluronic acid in cosmetics as safe, there was no explanation given of how it achieved “radiance” or “glow” in the skin, he said. “The answers do not address the questions being asked . . . and it is an acid in all senses of the word.”

Aarathi Prasad, a biologist from Sense About Science, said that the claims for commercially available creams were: insulting to people’s intelligence. “There may be evidence to justify using some of these chemicals — but not in products claiming to improve the signs of ageing or having an active effect on the skin. The companies are taking the real science out of context so it becomes bad science.”

Dr Moss said that if cosmetics claimed to have an active effect on lower reaches of the skin, they should be classed as medicines and subject to much tighter regulation and testing.

Dr Prasad said: “If using these products makes people feel better or perceive that they look better then by all means they should use them, but there is scant scientific evidence to justify that effect.”

L’Oréal, which markets both the Garnier brand and products under its own name, said yesterday: “Science is always at the heart of L’Oréal’s products. The company employs almost 3,000 scientists and registers around 600 patents each year.”

Procter & Gamble, the pharmaceuticals giant that makes and markets the Olay brand, said in a statement: “We agree that the answer to the question reported in Which? magazine was not completely accurate and we will address this with our consumer relations team.”

Fact or fiction?

Olay Regenerist

Which? researcher Are the ingredients natural?

Customer service “Pentapeptides are fragments of molecules. They’re found naturally throughout the body so they originate from the body.”

Sense About Science verdict “This can’t be right. Laboratory-made pentapeptides may be chemically indistinguishable from those that occur naturally, but be clear that they’re not extracting them from real cells.”

Garnier Nutritionist Omega Skin

Which? How will it help with the fine lines on my face?

Customer service “You have the rosehip and the magnesium that do that and also there’s another ingredient called lipopeptides and that is also another natural stimulant that helps the skin.

It makes the skin resilient and visibly younger.”

Sense About Science verdict “Certain lipopeptides can be potent stimulants – of the immune system. But stimulating the immune system is by no means the same as stimulating collagen formation. You cannot really link stimulation of the immune system with skin rejuvenation like this. I can’t think what else she may be referring to when she says it stimulates.”

L’Oreal Dermagenesis

Which? What is hyaluronic acid?

Customer service It’s not an actual acid. The product replumps, tautens and illuminates to give radiance to the skin.

Sense About Science verdict “This does not answer the question and does not explain what the acid does in any mechanistic sense. And it is an acid in all senses of the word.”

Source: Which?

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