One session lasts three to four months. Only a small amount goes into small muscles such as those at the mouth corners or nostrils, so the duration is similar to ordinary wrinkle treatment. People who make large expressions often use those muscles more, and it can wear off a little sooner.

Because only a small amount goes into a small muscle, a slight misjudgement of dose can make the expression look off. It usually settles after the first two or three weeks. Starting low and topping up at a two-week review is the safer approach, and the anatomy of each site has to be known precisely.

It appears over about two weeks. It reduces the movement of a single muscle, so the difference shows only in one specific action — a gummy smile, or the mouth corners turning down. The face at rest changes little, so you need to make that expression in the mirror to see the result.