Botox and Xeomin act by temporarily blocking the transmission of nerve impulses into muscle or temporarily paralyzing muscle. The toxin is diluted and injected into specific muscles to diminish or stop their activity. The amount used is less than 100 times less than a lethal dose and its effect remains localized. Diffusion to adjacent muscles is prevented by remaining in an upright vertical position (for injections to the face) for 2 to 3 hours after injection and injection of concentrated solutions. Diffusion to adjacent muscles can cause upper eyelid drooping, eyebrow drooping, lower eyelid drooping with tearing and swallowing problems.
In the aging face certain wrinkles (horizontal forehead lines, vertical frown lines between the eyebrows, crows feet lines) are caused by the action of underlying muscles and may diminish or disappear with paralysis or weakening of the muscle. It can also be injected into the skin to decrease perspiration in the armpits or palms.
The full effect of toxin injection takes 5 to 7 days to become visible and lasts 2 to 5 months. If injected to control perspiration it takes 2 or 3 days to become effective and can last as long as 12 to 18 months.
Occasionally there is mild pain and or bruising at the injection site that is temporary in nature.
Failure of wrinkle resolution can occur even if the requisite muscles are paralyzed due to either scar between the wrinkled valley and underlying structures or contraction of adjacent muscles that are recruited.