There's a lovely jar of night cream that's been sitting on my dresser for a month. According to the salesperson who spent a half-hour on the phone with me extolling its virtues, the cream will dig up the gunk that's clogging my pores, soak up excess oil, and "teach" my cells to make less of it.

Sounds fantastic, doesn't it? Too bad I'm too scared to use it.

The cream, which cost me $163 for half an ounce, is made by New York City-based Bionova. The company's website makes much of its "nano tech platform," and explana­tions of its products feature incomprehensible phrases such as "restoration of the malfunctioning biological information transfer." But details in plain English of how any of this would actually work are sketchy. And the sales­woman's explanation was similarly cryptic. The cream, she informed me, has various "nano complexes" in an exact ratio that is customized for my age, my gender, and my face's precise degree of oiliness--information gleaned from a number of probing questions she asked me.

How, I asked, did I know these tiny particles weren't going to creep under my skin and wreak havoc with my body? No, she assured me, the cream uses chemicals of a regular size, just in nano amounts. "See the difference?"

Not really. Scientists have for decades been doing experiments using chemi­cals in ­nanomolar quanti­ties, which simply means that they're ­extraordinarily dilute. So how was ­Bionova's product special? ­Alexander Sepper, Bionova's vice president for ­research and development, at first echoed the sales rep's statements. "Our nanotech slightly differs from the nano­tech that's made by most companies," he said. "We are not talking about nano­particles but about nano quantities."

I still didn't understand how the product could be called nanotech if it didn't actually use nano-sized particles. Sepper seemed to agree.

"You know, I should be honest with you. In the beginning, we called them simply biocomplexes," he said. "When nanotech came and everyone started to claim nanotech, nanotech, nanotech, of course the marketing people came to us and demanded that we have to accommodate the present situation. My understanding as a scientist is it's more marketing than science." According to Sepper, revenues from the product, which is sold in upscale stores such as Barneys, went up when Bionova began calling it nanotech. But when I pushed him a bit on the use of the word in marketing the cream, he quickly backtracked. "When I said we are using nano quantities, I thought you already knew that we are using nanoparticles. We are using nano quantities of the nanoparticles."

Confused yet? So was I. And so, it seems, is nearly everyone involved in the marketing of nanotech-based products. The fact is, Bionova is not an exception. Cosmetics are among the first consumer products to make use of nanotechnology--or at least to tout its benefits--but nobody, it appears, has a handle on exactly what is in these products, or how those mystery ingredients might affect people's health.

"You've got this situation where people are putting chemicals on the skin when we know very little about [nanotechnology's] safety," says Sally Tinkle of the North Carolina-based National Institute of Environmental Health Sciences, a division of the National Institutes of Health.

Check the Label

According to the Project on Emerging Nanotechnologies, which is run by the Woodrow Wilson International Center for Scholars in Washington, DC, nearly 400 products on the market claim to use nanotechnology, and 64 of those are cosmetics. And yet no one in the federal government is responsible for overseeing the safety of nanotechnology. "People are miniaturizing the particles, nanosizing them," says Andrew Maynard, science advisor for the Woodrow Wilson project, but he says that companies don't necessarily recognize the risks associated with the unique properties of nanoparticles.

That nanoparticles have unique properties is, of course, exactly the point of using them. When particles of some materials become extremely small, they can exhibit unusual--and interesting--physical and chemical characteristics. Gold nanoparticles, for example, are red and are much more reactive than larger chunks of the metal. Nanoparticle versions of some ingredients used in cosmetics are more stable, improve product texture, and are absorbed better.

Titanium dioxide and zinc oxide, which have been used for decades in sunscreens, are two examples of substances that benefit from nano­technology. Normally, each material forms a thick whitish coating, but nanosizing their particles makes them translucent--and, naturally, more popular among consumers. Some cosmetics companies use other nanoparticles, such as the 60-carbon soccer-ball-shaped molecules known as fullerenes or buckyballs. Zelens, a company based in London, England, claims that fullerenes in its skin cream help to suck up free radicals and slow aging.

But here's the rub: though some nanomaterials clearly have advantages, such materials might also pose risks. Will the smaller particles penetrate the skin? Can they clog airways and trigger immune responses? Will they lodge in the body's tissues, including the brain?

The simple answer is that no one knows. The U.S. Food and Drug Administration, the Environmental Protection Agency, and other federal agencies have research programs in place that may eventually answer some questions about the toxicity and environmental impact of nanoparticles. But such research will take time and a great deal more money. Through the federal government's National Nano­technology Initiative, the United States has spent an estimated $6.5 billion on various types of nanotechnology research, but only 4 percent of last year's budget went to assessing potential risks. In the meantime, the best the FDA can do is to say it has "no evidence at present to suggest that any of the materials currently in use pose a major safety concern."

Nano Mysteries

Unlike pharmaceuticals, cosmetics don't have to pass safety tests before they are sold. Cosmetics companies are free to sell their products without such testing--at least until a problem crops up. And so far, nanoparticles used in cosmetics seem to have a clean record.

John Bailey, executive vice president for science at the Cosmetic, Toiletry, and Fragrance Association, an industry trade group in Washington, DC, points out that sunscreens using titanium dioxide and zinc oxide nanoparticles have been used "safely and effectively by consumers for decades" and have been reviewed and approved by the FDA. But whether that record of safety can be extrapolated to other nanoparticles in other types of cosmetics is less certain. The danger is that conventional safety tests for cosmetics and other products might not pick up the special risks nanoparticles pose.

For example, NIH's Sally Tinkle has found that under certain conditions--if the skin is stretched a certain way or rubbed with enough force--nanoparticles can move below its top, dead layer. If the skin has cuts and abrasions or has been damaged in some other way, particles can get through to the layers underneath. "That's well established," says Tinkle. What happens once these particles reach the bloodstream is unclear. Some studies have found that smaller particles are cleared faster than larger ones and so are safer, but others suggest that once inside the body, nanoparticles travel through the blood, lodge in the lungs and brain, and accumulate over time, with effects that are still poorly understood.

Definitive answers to these toxicity questions may take some time to emerge. But given that nanoparticles behave differently from their larger counterparts, it makes sense to have a regulatory system that is able to recognize this size-dependent behavior. And it makes sense to provide regulatory oversight based on the unique chemistry of nanoparticles.

That kind of oversight might not be welcomed by the cosmetics industry, but without it, the entire promising field of nanotechnology could be in danger. If a safety problem is associated with a cosmetic product marketed for its nano ingredients (even if it doesn't really have any), the public perception of nanotech could be affected more generally. In Germany, there's already been one scare with a spurious nano product. In March 2006, after the "Magic Nano" spray bathroom cleaner was released, a number of people who had used it fell ill. Amid the confusion that followed, nobody, including the manufacturers, seemed to know exactly what was in the product. But the damage to nanotech's reputation had been done. "What it really highlights is the confusion about what people actually mean by the terms," says Maynard. "We need transparency in this whole area."

In Bionova's case, I'm still not sure whether the cream on my dresser contains any nanoparticles, and if it does, whether they will help or hurt me. Since the small dark-blue jar arrived, salespeople from the company have called me four times--ostensibly to check on whether I have any questions. During the first call, the sales rep told me that for the first few days of use, when the cream is opening up my pores and cleaning them out, "your skin is going to look aggravated. It's going to look itchy; it's going to look flaky."

I've yet to do more than smell the cream, and I doubt I ever will, so I won't know whether glowing skin would follow the flakiness, as the salesperson assured me. No matter how lovely the jar is or what lofty promises are made on behalf of its contents, the specter of tiny little nano-whatevers making their way through my body is enough to keep me away.