Credit: Christian Darkin/Photolibrary

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They call to us with a siren's song from the pharmacy shelf. Alluringly packaged in pure and clinical colours, the beauty creams and serums promise to erase the very signs of ageing. They're hard to resist. And when, despite our better judgment, we zoom in for a closer look, the elegant embossed gold-lettering reveals a dazzling list of scientific claims. Everything from 'cellular renewal' and 'DNA protection' to lists of complex chemical formulations and biological buzzwords.

But is it really science or just pseudo-scientific snake oil?

There's no doubt many of the ingredients have potent effects in the test tube. But do they do anything when applied to wrinkled human skin? It turns out there's simply no easy way to find out. For cosmetics companies, the name of the game is: keep things as murky as possible.

BARRIE FINNIN, a professor at Monash University's college of pharmacy in Melbourne, and PhD student Anita Schneider, recently tested a new wrinkle cure. Twice daily, 20 male and female volunteers applied a liquid containing Myoxinol, a patented extract of okra (Hibiscus esculentus) seed, to one side of their faces. On the other side they applied a similar liquid without Myoxinol. Every week for a month their wrinkles were tested by self-assessment, photography and the size of depressions made in silicon moulds. The results were impressive. After a month the depth and number of wrinkles on the Myoxinol-treated side were reduced by approximately 27 per cent.

But Finnin's research, commissioned by a cosmetics company, is unlikely to be published in a scientific journal. It's hard to even find studies that show the active ingredients in cosmetics penetrate the skin, let alone more comprehensive research on their effects. Even when rigorous studies are commissioned, companies usually control whether the work is published in the traditional scientific literature.

Welcome to the conundrum of 'cosmeceuticals'. These are a new generation of products that are said to actually banish wrinkles, rather than merely disguising them. And they are doing great business. In 2004, Americans bought US$6.4 billion (around A$7.2 billion) worth of cosmeceutical skincare products.

And competition is stiff: cosmeceutical companies are competing with plastic surgery procedures that are less traumatic than ever. These days, youth-seekers can have a lunchtime Botox injection to iron out wrinkles, or a shot of Restylane to fill them, or a series of laser treatments to regenerate deeper tissue pinhole by pinhole.

According to the cosmeceutical marketing machine, their new active ingredients produce the same results without the hard edge of surgery. Paradoxically, however, they don't want to 'prove' that their ingredients work. If they did, that could put them squarely in the sights of drug regulatory agencies. And that's the last thing they want. "It's a Catch-22 situation," says Finnin.

The costs of marketing a cosmetic are in the hundreds of thousands of dollars already; the costs of bringing a drug to the market are in the hundreds of millions. Pretty much all a cosmetics manufacturer has to do is mix up a batch of chemicals, and as long as they're all on an approved cosmetics register, the cream can go on sale the next day. By comparison, a new drug has to run a gauntlet of trials to prove it is safe and effective. And before governments will issue a licence, the drug has to be shown to be more effective than existing products.

Just as washing powders are required by law to live up to their claims, so too are skincare products. In May 2007 the makers of Lancôme, Clinique, Estée Lauder, L'Oréal and Payot were ordered to to withdraw advertisements by the Australian Therapeutic Goods Authority after the ads were found to contravene advertising codes. So companies walk a fine line: their claims need to be suggestive enough to ensnare consumers, but not so assertive they get nabbed by the regulators. "The answer is to use artful wordsmiths – the things stated on the label lead people to their own conclusions," says Finnin.

But many companies make outlandish claims and regularly receive warning letters from regulatory authorities such as the U.S. Food and Drug Administration. "Most companies are willing to take the risk," says dermatologist Chris Zachary at the University of California, Irvine. "The chances of getting caught are slim and even then, the official sanctions take years to be rendered. Larger companies prefer to pay a fine as the cost of doing business." And their regular legal defence is that consumers 'understand' their claims are not supposed to be taken seriously. So while the companies play a cat and mouse game with regulators, consumers are left in the dark.

SKINCARE PRODUCTS traditionally beautify in a superficial way: creams sit on the surface and create a barrier to prevent skin from drying. Alpha hydroxy acids or abrasives help slough off the scaly outer layers to leave skin smoother. Humectants, such as hyaluronic acid, urea or glycerol, attract water and can plump up the outer layer of the skin. Since these products don't affect the body's inner structure or function, they don't have to meet the requirements that pharmaceuticals do. But none of these products can reverse the ravages of ageing in the way that surgery can. This is where cosmeceuticals step in, with their more potent active ingredients, and correspondingly bold claims.

Dr LeWinn's 'Perfection Peptide P3', Payot's 'Bioxilift', Lancôme's 'Pro-Xylane' – the latest cosmetic ingredients sound like they come from a mad scientist's lab. Still, browsing the pharmacy shelves or the department store counters, it's difficult not to respond with a glimmer of genuine hope. Has science actually found a way to erase those crow's feet and Joker-esque smile lines?

One thing is for sure: the active ingredients of cosmeceuticals are based on an advanced understanding of the science of skin ageing.

Skin can be likened to a thin sheet spread across an inner-sprung mattress. When the mattress is new, the sheet lies flat and smooth. But as the mattress ages, its springs and struts break, the stuffing slowly disintegrates, and the sheet sags and wrinkles.

The thin sheet is the skin's epidermis (see diagram). Just 0.02 mm thick on the face, the epidermis is made up of cells called keratinocytes, glued together by an extracellular matrix. The epidermis is continually regenerated by stem cells at its base. These spawn new keratinocytes, which move up, and after a month, slough off – producing the major ingredient of house dust. Along the way, melanocyte cells infuse keratinocytes with the pigment melanin, to a degree dependent on their UV exposure.

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