Revolutionary skin care that accelerates normal cell renewal rate," read the label on Avon's Momentum skin cream. "It helps fresh new skin cells surface faster . . . Helps prevent lines and wrinkles . . . Works beneath skin's surface to help prevent cell destruction caused by ultraviolet rays and to help maintain the integrity of fresh, new cells . . . Skin will begin to function younger in 14 days."

Sound too good to be true? That's what the federal government thought, which is why the Food and Drug Administration has asked Avon -- and more than 40 other cosmetic manufacturers -- to refrain from making what the agency considers "outrageous claims" for their anti-aging skin creams.

But according to some cosmetic scientists, those claims aren't outrageous at all. They say that new formulations do penetrate to the deepest layers of the skin and affect cell turnover rate, new blood vessel development and membrane permeability -- all the biological functions that make skin look and feel the way it does. Some of these creams, according to scientists who work for cosmetic companies, are doing what creams could never do a generation ago: making skin biologically younger.

And that's the new wrinkle in discussions about anti-aging skin products. If the creams don't work, then manufacturers are making false or misleading claims. But if they do work, then the companies may be overstepping the bounds of traditional cosmetics and manufacturing products that behave more like drugs. So far, there is no consensus about whether or not the products work; FDA officials say there is no independent proof that they do anything more than sit on the skin.

But the possibility that these products have the biological effect manufacturers claim raises questions of whether these products are best classified -- and therefore regulated -- as drugs, as cosmetics or as a hybrid with the newly minted name of "cosmeceuticals."

"A whole host of products falls between the classic definitions of either a cosmetic or a drug: sunscreens, anti-wrinkle creams, skin firmers, astringents, products with disease prevention claims," said Rep. Ron Wyden (D-Ore.), who yesterday released a Congressional Research Service report on cosmeceuticals. "So we've got a choice: either shore up the cosmetic definition to make it meaningful, or put more and more of these products which may alter cell structure into the drug category."

A third option, as outlined in the report, is to establish a new regulatory standard for cosmeceuticals that falls somewhere between the standards for cosmetics and pharmaceuticals.Drug, Cosmetic or a Hybrid?

The legal definition of a cosmetic implies that the product is harmless. According to the 52-year-old Food, Drug and Cosmetic Act, a cosmetic is a substance intended "to be rubbed, poured, sprinkled, sprayed on, introduced into, or otherwise applied to the human body for cleansing, beautifying, promoting attractiveness, or altering the appearance."

A drug, by comparison, deliberately changes the way the body works. The same law defines a drug as a substance "intended to affect the structure or any function of the body." This is the purported action of many of the latest skin care creams.

A cosmeceutical, as its name implies, is a mixture of the two. Albert Kligman, the University of Pennsylvania dermatologist best known as the inventor of Retin-A, is credited with creating the term, which he defines as "an agent that has both cosmetic and drug effects, or a topical preparation that is neither pure drug nor pure cosmetic."

In a way, anything applied to the skin theoretically could qualify as a drug. Even water can affect the structure or any function of skin. As cosmetics researcher Gary Grove notes, sprinkling water on the skin will alter its electrical properties, its suppleness, its ability to be penetrated by certain ingredients. But obviously the writers of the Food, Drug and Cosmetic Act never intended water to be considered a drug.

"The key seems to be 'intended use,' " said Grove, whose Skin Study Center in Broomall, Pa., tests new products for the cosmetics industry. "You could have exactly the same product in two different packages, and, depending on what the labeling says, it could be considered a cosmetic or a drug."

If the label says a cream "produces a healthy, rosy glow" or "brings back that peaches-and-cream complexion," it mentions only appearance and qualifies as a cosmetic, Grove said. "But if {the label} says it enhances blood flow, that's a medical claim," said Grove, and the product would be considered a drug -- even if blood flow is enhanced solely to improve appearance. In the second case, Grove said, the rosy glow is merely "the cosmetic consequence of the physiological effect."

Classifying cosmetics as drugs is not without precedent. According to Michael J. Petrina, vice president of the Cosmetics, Toiletries and Fragrance Association, a Washington-based trade group, several cosmetic products are already regulated as over-the-counter drugs, among them sunscreens, anti-perspirants, dandruff shampoos and fluoridated toothpaste.

"But our member companies still haven't decided whether anti-aging creams should be treated as drugs or cosmetics, or what language to use to change the law," Petrina said. What they all agree on, he added, is that "there would be serious effects on the industry if these products were to require pre-market clearance by the Food and Drug Administration."

And there is no dispute that cosmetics are a lucrative business: $18 billion a year, industry officials estimate.

Sales of "skin renewers" and other anti-aging preparations, which currently account for an estimated $2.5 billion in sales annually, are expected to grow as the huge baby boom generation moves from thirtysomething to fortysomething, and beyond.

Under current regulations, no proof of safety or efficacy is required for a new cosmetic. As one FDA document noted, "With the exception of color additives and a few prohibited ingredients, a cosmetic manufacturer may . . . use essentially any raw material as a cosmetic ingredient and market the product without approval."

Nor is there any requirement for a cosmetic manufacturer to report adverse effects to the FDA once the product is in use.

In contrast, a new drug requires a lengthy process, involving up to seven years of testing for evidence of safety and efficacy and the expenditure of millions of dollars before it can be marketed. In addition, there is a protracted period of post-market surveillance to monitor long-term hazards.

A Regulatory Void

To date, the FDA has limited its regulation of "anti-aging creams" and "cell renewers" to a debate over labeling claims. Such promises suggest "that the products are adequate and effective for cell renewal, reversal of signs of facial aging, increased collagen production, cell repair and other claims," the FDA wrote in one of the first regulatory letters, sent to Avon in April 1987. "Because of such claims, these products are regarded as drugs."

The names of the products cited by the FDA are suggestive: Among them are BioAdvance Beauty Recovery System, Lift Serum Anti-Wrinkle Complex, Prescriptives Line Preventor and Momentum Cell Energizing Formula with Daytime Defense Complex.

"Every one of these new products has a name which conjures up significant medical claims," said Wyden. "They're all called 'Bio something.' Using words like 'bio' and 'cell' coveys a message that goes well beyond the question of beautification and superficial attractiveness."

In response to the regulatory letters, most of the companies changed their labels, according to Daniel L. Michels, director of the Office of Compliance for FDA's Center for Drug Evaluation and Research.

Avon altered the label on Momentum as a result of the FDA objections. Alex Znaiden, Avon's director of skin care, said that since the product contains a sunscreen, it was already regulated as an over-the-counter drug. Therefore, the current label emphasizes its ultraviolet protection and does not mention any other biological effect.

The new label says that the product "shields and protects against surface skin damage" and with "regular use may help prevent lines and wrinkles due to overexposure of the sun."

Not all manufacturers have been so responsive to the FDA, whose officials acknowledge that monitoring the cosmetics industry is not a high priority. "I don't keep up on this on a day-to-day basis," Michels said. "Frankly, this issue is not something that FDA has unleashed all its resources on."

The reason, according to former FDA Commissioner Frank Young, is simple: "To tell you the truth," he told a congressional subcommittee on cosmetics safety in 1988, "our agency is dealing with overwhelming problems: AIDS, salmonella in eggs, pesticides and toxic chemicals in foods. Cosmetics are . . . on balance safer than the other products we regulate." Beauty That May Be More Than Skin Deep

The FDA's approach to cosmeceutical regulation makes some scientists uneasy. Changing the label without changing the product, said Grove, who tests products for the cosmetics industry, does not address the fact that many new products can really do what they say they can. Their ability to permeate the skin and change cell structure still makes them closer to drugs than to cosmetics, he said, despite what the labels say.

He cited the Estee Lauder product called Night Repair Cellular Recovery Complex as an example of a skin cream that appears to be a cosmeceutical. The product's label says it can undo the DNA damage caused by the sun. "Laboratory tests show a 37 to 38 percent rate of increase in the natural repair of cells" damaged by ultraviolet light exposure, according to the label.

"If such claims are true," said Grove, "this is a real medical breakthrough, something that can help people with medical syndromes like xeroderma pigmentosum, {a rare disease resulting from extreme sun sensitivity that causes premature aging} caused by a problem with DNA repair."

Similar breakthroughs may be occurring throughout the cosmetics industry. Some products contain ingredients that can switch on fibroblasts, the cells that manufacture the deep-layer skin cells -- collagen and elastin -- that provide structural support to the skin and that weaken with age.

Others use a special fatty envelope called a liposome to penetrate the stratum corneum, the surface layer of dead skin cells, and deliver active ingredients directly to the dermis, where new cells are formed. And some can speed the sloughing of surface skin cells to hasten the appearance of fresh cells.

"More sophisticated raw materials are available to manufacturers today that they just didn't have years ago," said Charles Fox, a Fairlawn, N.J., cosmetic chemist who is an industry consultant. "There are materials that can stop or slow the flow of {oil} in skin that is too oily or accelerate it for skin that is too dry. There are enzymes that can affect cell repair. And there are ways to deliver these materials to the living part of the skin, beneath the stratum corneum, so they do penetrate more deeply."

Avon's Znaiden says his company uses vitamin A alcohol, collagen promoters and anti-oxidants in skin-care products like Bioadvance and Collagen Booster. "And we use natural products like grape seed oil and sunflower seed oil, which contain high amounts of linoleic acid needed for good water retention of the skin."

The downside of the ability to change skin structure and function may be the potential to cause problems in the skin and elsewhere in the body. Many women expect transient rashes or irritations when they try a new cream or lotion. But an anti-aging cosmeceutical, some experts theorize, could cause more serious side effects, such as dizziness, headaches or shortness of breath, if the product penetrates deeper into the skin. The Dangers of Cosmetics

To date, the only documented cases of cosmetics-associated health risks have been among hairdressers and manicurists, whose occupational exposure to cosmetic ingredients is unusually high. According to the professional hair care and beauty trades division of the United Food and Commercial Workers International Union, cases of neurological damage, skin disease, upper respiratory infections and miscarriages reported by their members seem to be associated with exposure to cosmetics.

Some anti-aging creams might have different -- and unanticipated -- side effects. If a cream increases the rate of skin cell turnover, for instance, some scientists wonder whether the new cells would be normal or abnormal. "How much skin turnover is good and how much is harmful?" Fox asked. "After all, think of what psoriasis is: the skin turning over so rapidly that it's not forming normal skin."

These possible health hazards remain speculative, largely because no one seems to be interested in investigating the risks of cosmeceuticals. "Wyden is the only one in Congress who's really looking into cosmetic safety," said Katherine Isaac, a staff researcher at Ralph Nader's Center for the Study of Responsive Law and author of the center's 1986 report, "Being Beautiful."

"Cosmetics aren't considered that important," she said. "The cosmetic division of the FDA doesn't have the staff to keep on top of things. And cosmetics are not that expensive, so the Federal Trade Commission doesn't place a high priority" on regulating advertisements for the newest generation of creams.

But with enough people putting enough new potions on enough faces, some problems are bound to occur. Since her book was published, Isaac said, she has received dozens of letters detailing adverse reactions to various skin care products, including anti-aging creams.

"The worst was from a model who started using a new line of skin care products because she was going to advertise it," said Isaac. "She had a really bad reaction but she continued to use it, because the manufacturer kept telling her it was all part of the process of deep nourishment." Even though she has long since stopped using the creams, the model told Isaac, she is still plagued by severe and apparently permanent scars.

The big question now is how cosmeceuticals should be regulated. The Congressional Research Service has proposed three options: more stringent regulation of all cosmetics, more precise classification of products as either cosmetics or drugs or both, or a new category "for cosmetics with drug characteristics," which might subject cosmeceuticals to pre-market approval and safety testing.

Wyden said he plans to develop legislation that would set new standards for regulation of cosmeceuticals. "I'd like some clarity in the law and some understood definitions," he said.

"We've got to get beyond this method of creating definitions as you go, case by case, and instead make some fundamental decisions. It's time to bring the definition of cosmetics into the 1990s. We've got an $18 billion industry making bolder and bolder claims, governed by a statute that was written in the 1930s."

But while the regulators and manufacturers haggle over how best to regulate and promote these products, consumers may have a far more personal concern. What Baby Boomers with a few wrinkles most want to know: Are any of these anti-aging creams worth using?

Grove, who is in his forties, is skeptical. He has tested most of the cosmeceuticals now on the market using fiber-optics, fluorescent dyes and moisture and elasticity gauges. But even though he has measured clear improvements with these products in moisture retention and skin cell structure, he said neither he nor his wife uses them. Instead, they refrain from sunbathing and wear a high-protection sunscreen year round.

Avon's Znaiden, though, said he and his wife use his company's Collagen Booster. "Every single person I have given Collagen Booster to has come back for more," said Znaiden, who is 43. "It's amazing what a difference it makes. I think of it as the first of the 21st-century skin-care products now being introduced."

Grove remains dubious. His biggest fear about the new super-creams "is that they leave you with the impression that you don't have to take care of your skin. They make it sound like you can damage your skin all you want, and all you have to do is splatter on some of this magic cosmeceutical #506, and you'll undo it all."