A system for administering pain-free injections includes an electric current source having at least two electrodes attached adjacent an injection site, the electric current source producing a variable numbness pattern and providing a frame of reference for identifying a plurality of sub-areas of the injection site; and a probe applied to the plurality of sub-areas of the injection site for pain-response testing, wherein one or more areas of numbness in the variable numbness pattern are identifiable according to the plurality of sub-areas of the injection site. A fence may be removably applied to the injection site and provide a frame of reference for identifying a plurality of sub-areas of the injection site, and may aid in identifying one or more areas of numbness in the variable numbness pattern. The fence may be removably applied to the injection site via a belt or manual pressure.