The treatment of facial expression lines with botulinum toxin A is a special field of wrinkle correction as this method not only allows existing lines to be corrected but also treats the cause of the wrinkles, that is excessive expressions.
Botulinum toxin A is a protein produced by bacteria. It has been used successfully in the treatment of spastic paralysis, facial and eye cramp for many years. Botulinum toxin A inhibits the transmission of specific nerve impulses. It is injected just under the surface of the skin into the small expressive muscles and causes precisely these muscles to relax over the following weeks.
As you can decide from the outset which small expressive muscles are to be injected and with what dosage, an undesirable mask-like face does not normally result. In the days following treatment the muscle tension in the treated areas decreases, leading to a clear relaxation of the skin and to a reduction in wrinkles. The other facial muscles are not affected. Botulinum toxin A is particularly suitable for smoothing out worry lines and frown lines. 

Injections should not be carried out on patients with certain conditions (e.g. generalised disorders of muscle activity) or certain virus infections (e.g. herpes). Botulinum toxin A should also not be administered during pregnancy or breastfeeding – purely as a precaution.
Certain medications and substances should not be taken before treatment. Aminoglycoside antibiotics can significantly increase the effect of botulinum toxin A, for example. Taking blood-thinning medication or acetylsalicylic acid (e.g. Aspirin), vitamin E, ginkgo or garlic during treatment may lead to slight bruising at the injection sites. As this therapy is not approved for use on persons under the age of 18, such persons are not usually treated.

Wrinkles which are not caused by muscle activity (expressions) but are due to the aging of the skin or UV damage usually respond better to other forms of treatment (e.g. laser treatment or wrinkle injections with filler material).
In the event that some lines remain visible in the area of treatment after deeper wrinkles have been treated with botulinum toxin A, botulinum toxin A injections can be combined with any other method of line correction.