The decision by the Food and Drug Administration is likely to further boost the popularity of Hollywood's favorite skin smoother.
The FDA ruling allows Allergan Inc. to advertise Botox's age-defying benefits for the first time in the United States.
The company previously could not promote that use, although doctors could inject Botox to fight wrinkles because it was on the market for medical purposes.
Allergan plans to start advertising Botox Cosmetic to doctors and consumers in magazine and television advertisements in the coming months, company spokeswoman Christine Cassiano said.
Even without promotion, Botox injections ranked as the most common cosmetic procedure in the U.S. in 2001 as they became the latest craze among Hollywood stars, television news anchors and others trying to soften signs of aging.
Botox is a purified form of the toxin that causes botulism, or food poisoning. Frown lines, those furrows between the eyebrows, are typically formed by excessive contraction of two forehead muscles. Injecting small doses of Botox into those muscles can weaken or paralyze those muscles, thus temporarily improving the appearance of the wrinkles.
Botox is "that rare procedure where anyone who gets it is overwhelming pleased ... there's universal satisfaction," said Dr. Philip Miller, a facial plastic surgeon at New York University School of Medicine.
First approved in 1989 as a therapy for eyelid muscle spasms, Botox received FDA clearance Monday for temporarily improving the appearances of vertical frown lines between the eyebrows. Shots take 10 to 15 minutes, and benefits appear within days.
But the look does not last. In clinical studies, lines were softened for up to 120 days. Repeat treatments cost between $200 and $1,000. Botox should not be injected more than once every three months, the FDA recommended.
In studies, post-injection reactions included headache, respiratory infection, flu-like symptoms, droopy eyelids and nausea, the FDA said. Fewer than 3 percent of patients experienced other problems - pain in the face, injection-site redness and muscle weakness - that could last several months.
In 2001, Americans underwent more than 1.6 million procedures with Botox or a similar product, Myobloc, according to the American Society for Aesthetic Plastic Surgery. That was a 46 percent increase from 2000 and the top cosmetic procedure of 8.5 million performed in 2001.
Botox sales last year were about $310 million, Allergan said, but the company did not say how much of that came from cosmetic use. The product's popularity is expected to grow once the new ad campaign starts, industry analysts said.
"People spend a lot of money on cosmetic products that are not proven to actually be effective. The beauty of this product is that there is clinical data measuring its effect," Merrill Lynch analyst Gregg Gilbert said.
"You've got an aging population. You've got low penetration rates for Botox as it is for cosmetic purposes, and you look at what direct-to-consumer ads can do for a product and you are looking at some pretty substantial growth most likely," Banc of America Securities analyst Tim Chiang said.