It is temporary, and within a few months the doctor can re-inject the same areas. There is some proof it is less effective as more injections are given. However many physician feel the opposite is true and that with repeated use of low doses the muscle actually thins and weakens. In addition, through a process of re-education the patient can break the habit of contracting certain muscles that has developed over many years. In many people several areas are injected simultaneously.
Most doctors like to limit the amount of toxin injected at one time.
Serious side effects are uncommon although there is potential for more serious complications if large amounts are injected. The most common problem is bruising and discomfort for a few days. After the injection it is recommended that no heavy exercise or lifting is performed for a few hours. You can apply makeup within a few hours. These injections are not a substitute for a facelift, or other surgery.