Tissue expanders are relatively painless. Skin and many of your soft tissues can be stretched with relatively little to no pain at all.
Think about when you eat a large meal like Thanksgiving and your belly sticks out. If you measure your waist it's probably a few inches larger than it was just before Thanksgiving. Now imagine doing that every week for a few months. You're belly would get quite alot larger with realtively little pain. (This is not an experiment you should try :)) Your skin has a natural give to it. If you keep slowly expanding or stretching it out over time, then you actually grow more skin.
There is a little discomfort with each expansion, i.e. each time they fill up the expander with more saline. But it shouldn't be painful. If it's too painful, this may indicate that the expander has been filled up too much and that it's causing too much stress on your overlying tissues. The discomfort should respond to tylenol or ibuprofen and go away relatively quickly, i.e. within a few hours.
