Colonics should not be painful, however depending on your levels of toxicity and blockages from waste in the colon you could experience some discomfort during the treatment.
These symptoms will ease each time you have a treatment as the toxic load will be lessened. You can also feel some nausea during the treatment at times whilst the body is releasing waste but once you have removed the waste that feeling should go immediately.
After a treatment you should feel a lightness and a lot clearer in the head and some people experience improved energy straight after.