Botulinum toxin is an injectable denervating agent often referred to as a muscle relaxant. This is a misnomer. Rather than relaxing the muscles, it temporarily weakens or paralyzes them, smoothing frown lines. Only lines caused by muscle contractions will be affected by botulinum toxin injections. Since the affected muscles no longer contract, there are limited areas of the face where this can be used. The most common locations for treatment are in the upper third of the face — on the frown line, crows' feet, and on the forehead lines.

Botulinum toxin is injected directly into the muscle, and anesthesia is not necessary. The toxin takes three to five days to take effect and lasts three to four months. Repeat treatment may be necessary after three to six months. When the effect begins to wear off, you will notice your wrinkles beginning to return.

Potential side effects for dermal injectables
As with all medical procedures that involve injection through the skin, there are certain risks and restrictions associated with the use of injectable facial dermal products. You should not use a product if you have a history of allergy to any of its ingredients. For some products, skin tests will be necessary to determine if you are allergic to the product. You should not use these products if you have an infection at the injection site. The most common side effects following an injection procedure include localized pain, tenderness, redness, bleeding and bruising. In addition, there may be other risks associated with a particular type of injectable that you should discuss with your doctor to fully understand these risks.