NGELINA UMANSKY, an owner of a day spa in San Francisco, has observed plenty of trends in cosmetic procedures over the years, from breast implants to collagen injections to glycolic acid peels and, more recently, Botox. These days, she says, all she seems to hear from her clients is talk of the cosmetic fillers that are supposed to work faster on facial flaws and last longer than Botox.

And it doesn't seem to matter that these products are not yet approved for use in the United States. Some American doctors have them shipped from abroad, where they are sold legally, and quietly administer them anyway.

"Safety is not a concern; they just want instant results," said Ms. Umansky, whose business, Spa Radiance, stays with more traditional beauty treatments, like facials, massages and manicures. Many other day spas, though, do offer Botox and other nonsurgical cosmetic procedures.

Cosmetic dermatologists and surgeons say that unrelenting consumer demand for treatment of wrinkles and sagging skin has fostered the development of a new generation of injectable cosmetics. Unlike Botox treatments, which reduce wrinkling by temporarily paralyzing muscles with injections of botulinum toxin, fillers plump up the face underneath the skin, filling in the wrinkles.

Dr. Richard G. Glogau, a clinical professor of dermatology at the University of California at San Francisco, said he expected that over the next several months, a half-dozen new injectable cosmetics would be approved or in the final stages of approval by the Food and Drug Administration and that about as many other products would also begin clinical testing.

Late last month, an F.D.A. advisory panel recommended approval of the filler product Artecoll, whose results are said to be permanent and which has already been available in several countries outside the United States. A final F.D.A. decision is expected in the next several months. Artes Medical of San Diego, the developer, says that it plans to sell Artecoll under the brand name Artefill. Similar products under F.D.A. review from other companies include Restylane, CosmoDerm and CosmoPlast.

"I predict that this field is going to get very crowded for awhile, and that only with time will these products sort themselves out as they gain clinical track records," Dr. Glogau said.

Last year, nonsurgical procedures accounted for about 77 percent of the nearly seven million cosmetic procedures — led by Botox treatments, which must be repeated regularly to maintain their benefits — that were performed in the United States, according to an annual report released last week by the American Society for Aesthetic Plastic Surgery.

Though they have yet to come to market, the new wrinkle fillers are already causing some confusion among consumers, which was why the plastic surgeons' organization said that it added a primer to its Web site (http://surgery.org) that explains the differences in the various injectable cosmetics. Some physicians, meanwhile, have privately begun to warn patients that virtually all the new products are still being evaluated for their exact effects, as well as how well they work relative to one another.

Cosmetic dermatologists say their biggest concern about permanent fillers, like Artecoll, for example, is that side effects might also be permanent. Artecoll relies primarily on tiny plastic particles to stimulate the body to produce its own collagen, while leaving the particles permanently embedded in the skin. So far, its side effects have been minor, according to Dr. Stefan M. Lemperle, the chief executive of Artes, adding that the filler has been tested on people with a variety of facial wrinkles.

Dr. Douglas Hamilton, a cosmetic dermatologist who is also an assistant clinical professor of dermatology at the University of California at Los Angeles, said that he has tested Artecoll on about 125 patients since 1997 as part of the F.D.A. clinical trials. While one of those patients experienced a slight elevation of the skin at the site of the injection, he said, the rest of the patients experienced, at most, a temporary redness at the injection site.

"It makes the treated area look like what it did before aging began, but eventually the body's clock starts ticking there again," Dr. Hamilton said.

Still, Artecoll's longer-lasting effects appeal to some people, among them at least two subjects of Dr. Hamilton's clinical tests — a 58-year-old antiques dealer from Southern California and his wife, 49, both of whom asked that they not be identified. "Those lines added 10 years to my face, but I didn't want to keep coming back to my doctor for something like collagen injections," the dealer said.

Physicians expect that Restylane will last longer than Botox, though not as long as Artecoll. Restylane contains a form of hyaluronic acid, which is found naturally in human skin and helps create volume and shape. The Swedish company Q-Med already sells Restylane — along with two sister products, Restylane Fine Lines and Perlane — in 60 countries.

Q-Med said that in clinical trials, Restylane was effective up to a year for treating wrinkles. But according to Dr. Glogau, patient tests with Restylane in the United States showed that it usually worked three and a half months to eight months, with results generally shorter-lived when it was injected into parts of the face where there were more muscular movements — around the lips, for example. By contrast, he said, Perlane worked eight to nine months, while Restylane Fine Lines was usually effective four to five months.

Dr. Glogau said that hyaluronic acid-based cosmetic procedures outside of the United States generally cost consumers $400 to $800 each. Botox, a product of Allergan in Irvine, Calif., lasts three to six months and costs an average of $400 a treatment. Collagen injections cost about $350 each and generally require a reapplication after three to five months. The main drawback, however, is that collagen treatments become less effective with time.

CosmoDerm and CosmoPlast, developed by Inamed in Santa Barbara, Calif., and sold outside the United States, are made from human collagen. Their main advantage, physicians say, is that they can be used without requiring patients to have skin tests now needed to determine whether they are allergic to collagen from bovine sources.

In January, Inamed also began clinical tests in the United States of another botulinum toxin product, Dysport. Cosmetic dermatologists say they expect that it will provide the same kinds of results as Botox.

Physicians warn that it's highly unlikely that any one of the newer injectable cosmetics will work the same in all people, or on all parts of the face. It's also unlikely, they say, that the new injectables will quickly phase out older products. Some data has already begun to suggest that Restylane, for example, is more effective at treating deep facial wrinkles when it is used with Botox or even collagen. Botox, meanwhile, is being officially studied to see how effective it might be on various parts of the face and neck.

Some physicians say they are concerned that Botox and the newer injectable products will be used indiscriminately. "One of my gravest concerns is that people are injecting Botox all over the face — on places like the lips, cheeks, chin, nose and neck — with increasingly unpleasant results like faces that are completely immobilized," said Dr. Seth Matarasso, an associate clinical professor of dermatology at the University of California at San Francisco.

Botox has been found effective in reducing the appearance of crow's-feet and furrowed brows by relaxing the muscles around the eyes and forehead.

 
MR. MATARASSO and other physicians are also concerned about the growing use of terms like "Botox alternative" and "Botox like" in marketing some procedures — especially on the Internet. Such treatments, they say, include everything from homeopathic remedies to surgery to snip out the so-called frown muscle that is between the eyebrows. "It's definitely buyer beware," Dr. Matarasso said.

Ms. Umansky, the San Francisco spa owner, is also worried. She says many people have already mentally moved beyond Botox. Over the last two decades, she said, she has seen many problems with trendy new cosmetic procedures, like silicone breast implants, as well as the allergies and dried out skin that she says many consumers have developed recently after using some wrinkle relievers.

"This is not about rushing out to do what your friends are doing," she said. "If there are consequences, you will be the one to live with them."