The science and philosophy behind reflexology is to balance the harmony between the physical and mental state of the body. To be at dis-ease; to have a disease,  is the body telling us that the harmony between the mind – body and soul is out of balance. Each organ and connective tissue has a correspondent reflex zone (acupressure point) in our feet.
To impose pressure , heat, on these points, these reflex zones are stimulated with the related organ , where the blockage will be relieved into a smooth (energy)  flow.
During the treatment, these blockages are experienced with sometimes an uncomfortable sensation at that particular point, either a light pain, itching or a prickling feeling.
During your course of treatment, sometimes the color of the skin changes and/or your calluses starts to  split, just to mention a few.   When these reactions are experienced, it tells the therapist what organ or connective tissues are affected.