Botox has been touted to relieve face wrinkles -- and now it has the government's stamp of approval.

The Food and Drug Administration approved Botulinum Toxin Type A -- known as Botox Cosmetic -- to temporarily improve the appearance of frown lines between the eyebrows.

The product's manufacturer, Irvine, Calif.-based Allergan, Inc., is now allowed to market Botox.

Small doses of Botox are injected into muscles, paralyzing or weakening them, which blocks the release of a chemical that causes muscles to contract.

Botox was first approved in December 1989 to treat two eye muscle disorders and in December 2000 to treat cervical dystonia.

In FDA studies, Botox injections reduced frown lines between the eyebrows to some extent for up to 120 days. Most of the patients in the study were female, and the majority were under 50 years old.

It is recommended that Botox Cosmetic be injected once every three months at most, and the lowest effective dose should be used.

The most common adverse side effects included headache, respiratory infection, flu syndrome, droopy eyelids, and nausea. Other, less frequent, side effects included pain in the face, redness at the injection site and muscle weakness. These reactions were generally temporary, but could last several months.

Because Botox Cosmetic is a prescription drug, it must be used carefully under medical supervision.

Additional Resources:

• Botox: How does it work?
• Read more about Botulinum Toxin
• Food and Drug Administration